diff --git a/.gitignore b/.gitignore
new file mode 100644
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--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,2 @@
+# generated by python builder
+*.pyc
diff --git a/README-bitbucket.md b/README-bitbucket.md
new file mode 100644
index 000000000..952717915
--- /dev/null
+++ b/README-bitbucket.md
@@ -0,0 +1,161 @@
+LeetCode
+========
+
+LeetCode C++ Solutions
+
+| Title | Solution | Add Date | Difficulty |
+| ----- | -------- | -------- | ---------- |
+|[Find Minimum in Rotated Sorted Array II](https://oj.leetcode.com/problems/find-minimum-in-rotated-sorted-array-ii/)| [C++](./src/findMinimumInRotatedSortedArray/findMinimumInRotatedSortedArray.II.cpp)|2014/10/20|Hard|
+|[Find Minimum in Rotated Sorted Array](https://oj.leetcode.com/problems/find-minimum-in-rotated-sorted-array/)| [C++](./src/findMinimumInRotatedSortedArray/findMinimumInRotatedSortedArray.cpp)|2014/10/15|Medium|
+|[Maximum Product Subarray](https://oj.leetcode.com/problems/maximum-product-subarray/)| [C++](./src/maximumProductSubarray/maximumProductSubarray.cpp)|2014/9/23|Medium|
+|[Reverse Words in a String](https://oj.leetcode.com/problems/reverse-words-in-a-string/)| [C++](./src/reverseWordsInAString/reverseWordsInAString.cpp)|2014/3/5|Medium|
+|[Evaluate Reverse Polish Notation](https://oj.leetcode.com/problems/evaluate-reverse-polish-notation/)| [C++](./src/evaluateReversePolishNotation/evaluateReversePolishNotation.cpp)|2013/11/27|Medium|
+|[Max Points on a Line](https://oj.leetcode.com/problems/max-points-on-a-line/)| [C++](./src/maxPointsOnALine/maxPointsOnALine.cpp)|2013/11/22|Hard|
+|[Sort List](https://oj.leetcode.com/problems/sort-list/)| [C++](./src/sortList/sortList.cpp)|2013/11/16|Medium|
+|[Insertion Sort List](https://oj.leetcode.com/problems/insertion-sort-list/)| [C++](./src/insertionSortList/insertionSortList.cpp)|2013/11/12|Medium|
+|[LRU Cache](https://oj.leetcode.com/problems/lru-cache/)| [C++](./src/LRUCache/LRUCache.cpp)|2013/11/9|Hard|
+|[Binary Tree Postorder Traversal](https://oj.leetcode.com/problems/binary-tree-postorder-traversal/)| [C++](./src/binaryTreePostorderTraversal/binaryTreePostorderTraversal.cpp)|2013/11/7|Hard|
+|[Binary Tree Preorder Traversal](https://oj.leetcode.com/problems/binary-tree-preorder-traversal/)| [C++](./src/binaryTreePreorderTraversal/binaryTreePreorderTraversal.cpp)|2013/11/5|Medium|
+|[Reorder List](https://oj.leetcode.com/problems/reorder-list/)| [C++](./src/reorderList/reorderList.cpp)|2013/11/2|Medium|
+|[Linked List Cycle II](https://oj.leetcode.com/problems/linked-list-cycle-ii/)| [C++](./src/linkedListCycle/linkedListCycle.II.cpp)|2013/10/30|Medium|
+|[Linked List Cycle](https://oj.leetcode.com/problems/linked-list-cycle/)| [C++](./src/linkedListCycle/linkedListCycle.cpp)|2013/10/28|Medium|
+|[Word Break II](https://oj.leetcode.com/problems/word-break-ii/)| [C++](./src/wordBreak/wordBreak.II.cpp)|2013/10/5|Hard|
+|[Word Break](https://oj.leetcode.com/problems/word-break/)| [C++](./src/wordBreak/wordBreak.cpp)|2013/10/4|Medium|
+|[Copy List with Random Pointer](https://oj.leetcode.com/problems/copy-list-with-random-pointer/)| [C++](./src/copyListWithRandomPointer/copyListWithRandomPointer.cpp)|2013/10/3|Hard|
+|[Single Number II](https://oj.leetcode.com/problems/single-number-ii/)| [C++](./src/singleNumber/singleNumber.II.cpp)|2013/10/2|Medium|
+|[Single Number](https://oj.leetcode.com/problems/single-number/)| [C++](./src/singleNumber/singleNumber.cpp)|2013/10/1|Medium|
+|[Candy](https://oj.leetcode.com/problems/candy/)| [C++](./src/candy/candy.cpp)|2013/9/30|Hard|
+|[Gas Station](https://oj.leetcode.com/problems/gas-station/)| [C++](./src/gasStation/gasStation.cpp)|2013/9/28|Medium|
+|[Clone Graph](https://oj.leetcode.com/problems/clone-graph/)| [C++](./src/cloneGraph/cloneGraph.cpp)|2013/9/24|Medium|
+|[Palindrome Partitioning II](https://oj.leetcode.com/problems/palindrome-partitioning-ii/)| [C++](./src/palindromePartitioning/palindromePartitioning.II.cpp)|2013/2/28|Hard|
+|[Palindrome Partitioning](https://oj.leetcode.com/problems/palindrome-partitioning/)| [C++](./src/palindromePartitioning/palindromePartitioning.cpp)|2013/2/27|Medium|
+|[Surrounded Regions](https://oj.leetcode.com/problems/surrounded-regions/)| [C++](./src/surroundedRegions/surroundedRegions.cpp)|2013/2/21|Medium|
+|[Sum Root to Leaf Numbers](https://oj.leetcode.com/problems/sum-root-to-leaf-numbers/)| [C++](./src/sumRootToLeafNumber/sumRootToLeafNumber.cpp)|2013/2/18|Medium|
+|[Longest Consecutive Sequence](https://oj.leetcode.com/problems/longest-consecutive-sequence/)| [C++](./src/longestConsecutiveSequence/longestConsecutiveSequence.cpp)|2013/2/13|Hard|
+|[Word Ladder II](https://oj.leetcode.com/problems/word-ladder-ii/)| [C++](./src/wordLadder/wordLadder.II.cpp)|2013/2/10|Hard|
+|[Word Ladder](https://oj.leetcode.com/problems/word-ladder/)| [C++](./src/wordLadder/wordLadder.cpp)|2013/2/10|Medium|
+|[Valid Palindrome](https://oj.leetcode.com/problems/valid-palindrome/)| [C++](./src/validPalindrome/validPalindrome.cpp)|2013/1/12|Easy|
+|[Binary Tree Maximum Path Sum](https://oj.leetcode.com/problems/binary-tree-maximum-path-sum/)| [C++](./src/binaryTreeMaximumPathSum/binaryTreeMaximumPathSum.cpp)|2012/11/7|Hard|
+|[Best Time to Buy and Sell Stock III](https://oj.leetcode.com/problems/best-time-to-buy-and-sell-stock-iii/)| [C++](./src/bestTimeToBuyAndSellStock/bestTimeToBuyAndSellStock.III.cpp)|2012/11/6|Hard|
+|[Best Time to Buy and Sell Stock II](https://oj.leetcode.com/problems/best-time-to-buy-and-sell-stock-ii/)| [C++](./src/bestTimeToBuyAndSellStock/bestTimeToBuyAndSellStock.II.cpp)|2012/10/30|Medium|
+|[Best Time to Buy and Sell Stock](https://oj.leetcode.com/problems/best-time-to-buy-and-sell-stock/)| [C++](./src/bestTimeToBuyAndSellStock/bestTimeToBuyAndSellStock.cpp)|2012/10/30|Medium|
+|[Triangle](https://oj.leetcode.com/problems/triangle/)| [C++](./src/triangle/triangle.cpp)|2012/10/29|Medium|
+|[Pascal's Triangle II](https://oj.leetcode.com/problems/pascals-triangle-ii/)| [C++](./src/pascalTriangle/pascalTriangle.II.cpp)|2012/10/28|Easy|
+|[Pascal's Triangle](https://oj.leetcode.com/problems/pascals-triangle/)| [C++](./src/pascalTriangle/pascalTriangle.cpp)|2012/10/28|Easy|
+|[Populating Next Right Pointers in Each Node II](https://oj.leetcode.com/problems/populating-next-right-pointers-in-each-node-ii/)| [C++](./src/populatingNextRightPointersInEachNode/populatingNextRightPointersInEachNode.II.cpp)|2012/10/28|Hard|
+|[Populating Next Right Pointers in Each Node](https://oj.leetcode.com/problems/populating-next-right-pointers-in-each-node/)| [C++](./src/populatingNextRightPointersInEachNode/populatingNextRightPointersInEachNode.cpp)|2012/10/28|Medium|
+|[Distinct Subsequences](https://oj.leetcode.com/problems/distinct-subsequences/)| [C++](./src/distinctSubsequences/distinctSubsequences.cpp)|2012/10/18|Hard|
+|[Flatten Binary Tree to Linked List](https://oj.leetcode.com/problems/flatten-binary-tree-to-linked-list/)| [C++](./src/flattenBinaryTreeToLinkedList/flattenBinaryTreeToLinkedList.cpp)|2012/10/14|Medium|
+|[Path Sum II](https://oj.leetcode.com/problems/path-sum-ii/)| [C++](./src/pathSum/pathSum.II.cpp)|2012/10/14|Medium|
+|[Path Sum](https://oj.leetcode.com/problems/path-sum/)| [C++](./src/pathSum/pathSum.cpp)|2012/10/13|Easy|
+|[Minimum Depth of Binary Tree](https://oj.leetcode.com/problems/minimum-depth-of-binary-tree/)| [C++](./src/minimumDepthOfBinaryTree/minimumDepthOfBinaryTree.cpp)|2012/10/9|Easy|
+|[Balanced Binary Tree](https://oj.leetcode.com/problems/balanced-binary-tree/)| [C++](./src/balancedBinaryTree/balancedBinaryTree.cpp)|2012/10/8|Easy|
+|[Convert Sorted List to Binary Search Tree](https://oj.leetcode.com/problems/convert-sorted-list-to-binary-search-tree/)| [C++](./src/convertSortedListToBinarySearchTree/convertSortedListToBinarySearchTree.cpp)|2012/10/2|Medium|
+|[Convert Sorted Array to Binary Search Tree](https://oj.leetcode.com/problems/convert-sorted-array-to-binary-search-tree/)| [C++](./src/convertSortedArrayToBinarySearchTree/convertSortedArrayToBinarySearchTree.cpp)|2012/10/2|Medium|
+|[Binary Tree Level Order Traversal II](https://oj.leetcode.com/problems/binary-tree-level-order-traversal-ii/)| [C++](./src/binaryTreeLevelOrderTraversal/binaryTreeLevelOrderTraversal.II.cpp)|2012/10/1|Easy|
+|[Construct Binary Tree from Inorder and Postorder Traversal](https://oj.leetcode.com/problems/construct-binary-tree-from-inorder-and-postorder-traversal/)| [C++](./src/constructBinaryTreeFromInorderAndPostorderTraversal/constructBinaryTreeFromInorderAndPostorderTraversal.cpp)|2012/9/30|Medium|
+|[Construct Binary Tree from Preorder and Inorder Traversal](https://oj.leetcode.com/problems/construct-binary-tree-from-preorder-and-inorder-traversal/)| [C++](./src/constructBinaryTreeFromPreorderAndInorderTraversal/constructBinaryTreeFromPreorderAndInorderTraversal.cpp)|2012/9/30|Medium|
+|[Maximum Depth of Binary Tree](https://oj.leetcode.com/problems/maximum-depth-of-binary-tree/)| [C++](./src/maximumDepthOfBinaryTree/maximumDepthOfBinaryTree.cpp)|2012/9/29|Easy|
+|[Binary Tree Zigzag Level Order Traversal](https://oj.leetcode.com/problems/binary-tree-zigzag-level-order-traversal/)| [C++](./src/binaryTreeZigzagLevelOrderTraversal/binaryTreeZigzagLevelOrderTraversal.cpp)|2012/9/28|Medium|
+|[Binary Tree Level Order Traversal](https://oj.leetcode.com/problems/binary-tree-level-order-traversal/)| [C++](./src/binaryTreeLevelOrderTraversal/binaryTreeLevelOrderTraversal.cpp)|2012/9/28|Easy|
+|[Symmetric Tree](https://oj.leetcode.com/problems/symmetric-tree/)| [C++](./src/symmetricTree/symmetricTree.cpp)|2012/9/23|Easy|
+|[Same Tree](https://oj.leetcode.com/problems/same-tree/)| [C++](./src/sameTree/sameTree.cpp)|2012/9/3|Easy|
+|[Recover Binary Search Tree](https://oj.leetcode.com/problems/recover-binary-search-tree/)| [C++](./src/recoverBinarySearchTree/recoverBinarySearchTree.cpp)|2012/9/1|Hard|
+|[Validate Binary Search Tree](https://oj.leetcode.com/problems/validate-binary-search-tree/)| [C++](./src/validateBinarySearchTree/validateBinarySearchTree.cpp)|2012/8/31|Medium|
+|[Interleaving String](https://oj.leetcode.com/problems/interleaving-string/)| [C++](./src/interleavingString/interleavingString.cpp)|2012/8/30|Hard|
+|[Unique Binary Search Trees II](https://oj.leetcode.com/problems/unique-binary-search-trees-ii/)| [C++](./src/uniqueBinarySearchTrees/uniqueBinarySearchTrees.II.cpp)|2012/8/27|Medium|
+|[Unique Binary Search Trees](https://oj.leetcode.com/problems/unique-binary-search-trees/)| [C++](./src/uniqueBinarySearchTrees/uniqueBinarySearchTrees.cpp)|2012/8/27|Medium|
+|[Binary Tree Inorder Traversal](https://oj.leetcode.com/problems/binary-tree-inorder-traversal/)| [C++](./src/binaryTreeInorderTraversal/binaryTreeInorderTraversal.cpp)|2012/8/27|Medium|
+|[Restore IP Addresses](https://oj.leetcode.com/problems/restore-ip-addresses/)| [C++](./src/restoreIPAddresses/restoreIPAddresses.cpp)|2012/8/7|Medium|
+|[Reverse Linked List II](https://oj.leetcode.com/problems/reverse-linked-list-ii/)| [C++](./src/reverseLinkedList/reverseLinkedList.II.cpp)|2012/6/27|Medium|
+|[Subsets II](https://oj.leetcode.com/problems/subsets-ii/)| [C++](./src/subsets/subsets.II.cpp)|2012/6/25|Medium|
+|[Decode Ways](https://oj.leetcode.com/problems/decode-ways/)| [C++](./src/decodeWays/decodeWays.cpp)|2012/6/25|Medium|
+|[Gray Code](https://oj.leetcode.com/problems/gray-code/)| [C++](./src/grayCode/grayCode.cpp)|2012/5/20|Medium|
+|[Merge Sorted Array](https://oj.leetcode.com/problems/merge-sorted-array/)| [C++](./src/mergeTwoSortedArray/mergeTwoSortedArray.cpp)|2012/5/20|Easy|
+|[Scramble String](https://oj.leetcode.com/problems/scramble-string/)| [C++](./src/scrambleString/scrambleString.cpp)|2012/4/30|Hard|
+|[Partition List](https://oj.leetcode.com/problems/partition-list/)| [C++](./src/partitionList/partitionList.cpp)|2012/4/30|Medium|
+|[Maximal Rectangle](https://oj.leetcode.com/problems/maximal-rectangle/)| [C++](./src/maximalRectangle/maximalRectangle.cpp)|2012/4/23|Hard|
+|[Largest Rectangle in Histogram](https://oj.leetcode.com/problems/largest-rectangle-in-histogram/)| [C++](./src/largestRectangleInHistogram/largestRectangleInHistogram.cpp)|2012/4/22|Hard|
+|[Remove Duplicates from Sorted List II](https://oj.leetcode.com/problems/remove-duplicates-from-sorted-list-ii/)| [C++](./src/removeDuplicatesFromSortedList/removeDuplicatesFromSortedList.II.cpp)|2012/4/22|Medium|
+|[Remove Duplicates from Sorted List](https://oj.leetcode.com/problems/remove-duplicates-from-sorted-list/)| [C++](./src/removeDuplicatesFromSortedList/removeDuplicatesFromSortedList.cpp)|2012/4/22|Easy|
+|[Search in Rotated Sorted Array II](https://oj.leetcode.com/problems/search-in-rotated-sorted-array-ii/)| [C++](./src/searchInRotatedSortedArray/searchInRotatedSortedArray.II.cpp)|2012/4/19|Medium|
+|[Remove Duplicates from Sorted Array II](https://oj.leetcode.com/problems/remove-duplicates-from-sorted-array-ii/)| [C++](./src/removeDuplicatesFromSortedArray/removeDuplicatesFromSortedArray.II.cpp)|2012/4/19|Medium|
+|[Word Search](https://oj.leetcode.com/problems/word-search/)| [C++](./src/wordSearch/wordSearch.cpp)|2012/4/18|Medium|
+|[Subsets](https://oj.leetcode.com/problems/subsets/)| [C++](./src/subsets/subsets.cpp)|2012/4/18|Medium|
+|[Combinations](https://oj.leetcode.com/problems/combinations/)| [C++](./src/combinations/combinations.cpp)|2012/4/18|Medium|
+|[Minimum Window Substring](https://oj.leetcode.com/problems/minimum-window-substring/)| [C++](./src/minimumWindowSubstring/minimumWindowSubstring.cpp)|2012/4/15|Hard|
+|[Sort Colors](https://oj.leetcode.com/problems/sort-colors/)| [C++](./src/sortColors/sortColors.cpp)|2012/4/8|Medium|
+|[Search a 2D Matrix](https://oj.leetcode.com/problems/search-a-2d-matrix/)| [C++](./src/search2DMatrix/search2DMatrix.cpp)|2012/4/6|Medium|
+|[Set Matrix Zeroes](https://oj.leetcode.com/problems/set-matrix-zeroes/)| [C++](./src/setMatrixZeroes/setMatrixZeroes.cpp)|2012/4/5|Medium|
+|[Edit Distance](https://oj.leetcode.com/problems/edit-distance/)| [C++](./src/editDistance/editDistance.cpp)|2012/4/4|Hard|
+|[Simplify Path](https://oj.leetcode.com/problems/simplify-path/)| [C++](./src/simplifyPath/simplifyPath.cpp)|2012/4/3|Medium|
+|[Climbing Stairs](https://oj.leetcode.com/problems/climbing-stairs/)| [C++](./src/climbStairs/climbStairs.cpp)|2012/4/3|Easy|
+|[Sqrt(x)](https://oj.leetcode.com/problems/sqrtx/)| [C++](./src/sqrt/sqrt.cpp)|2012/4/3|Medium|
+|[Text Justification](https://oj.leetcode.com/problems/text-justification/)| [C++](./src/textJustification/textJustification.cpp)|2012/4/3|Hard|
+|[Plus One](https://oj.leetcode.com/problems/plus-one/)| [C++](./src/plusOne/plusOne.cpp)|2012/4/2|Easy|
+|[Valid Number](https://oj.leetcode.com/problems/valid-number/)| [C++](./src/validNumber/validNumber.cpp)|2012/4/2|Easy|
+|[Add Binary](https://oj.leetcode.com/problems/add-binary/)| [C++](./src/addBinary/addBinary.cpp)|2012/4/2|Easy|
+|[Merge Two Sorted Lists](https://oj.leetcode.com/problems/merge-two-sorted-lists/)| [C++](./src/mergeTwoSortedList/mergeTwoSortedList.cpp)|2012/3/30|Easy|
+|[Minimum Path Sum](https://oj.leetcode.com/problems/minimum-path-sum/)| [C++](./src/minimumPathSum/minimumPathSum.cpp)|2012/3/28|Medium|
+|[Unique Paths II](https://oj.leetcode.com/problems/unique-paths-ii/)| [C++](./src/uniquePaths/uniquePaths.II.cpp)|2012/3/28|Medium|
+|[Unique Paths](https://oj.leetcode.com/problems/unique-paths/)| [C++](./src/uniquePaths/uniquePaths.cpp)|2012/3/28|Medium|
+|[Rotate List](https://oj.leetcode.com/problems/rotate-list/)| [C++](./src/rotateList/rotateList.cpp)|2012/3/27|Medium|
+|[Permutation Sequence](https://oj.leetcode.com/problems/permutation-sequence/)| [C++](./src/permutationSequence/permutationSequence.cpp)|2012/3/27|Medium|
+|[Spiral Matrix II](https://oj.leetcode.com/problems/spiral-matrix-ii/)| [C++](./src/spiralMatrix/spiralMatrix.II.cpp)|2012/3/27|Medium|
+|[Length of Last Word](https://oj.leetcode.com/problems/length-of-last-word/)| [C++](./src/lengthOfLastWord/lengthOfLastWord.cpp)|2012/3/27|Easy|
+|[Insert Interval](https://oj.leetcode.com/problems/insert-interval/)| [C++](./src/insertInterval/insertInterval.cpp)|2012/3/27|Hard|
+|[Merge Intervals](https://oj.leetcode.com/problems/merge-intervals/)| [C++](./src/mergeIntervals/mergeIntervals.cpp)|2012/3/26|Hard|
+|[Jump Game](https://oj.leetcode.com/problems/jump-game/)| [C++](./src/jumpGame/jumpGame.cpp)|2012/3/24|Medium|
+|[Spiral Matrix](https://oj.leetcode.com/problems/spiral-matrix/)| [C++](./src/spiralMatrix/spiralMatrix.cpp)|2012/3/24|Medium|
+|[Maximum Subarray](https://oj.leetcode.com/problems/maximum-subarray/)| [C++](./src/maximumSubArray/maximumSubArray.cpp)|2012/3/21|Medium|
+|[N-Queens II](https://oj.leetcode.com/problems/n-queens-ii/)| [C++](./src/nQueens/nQueuens.II.cpp)|2012/3/20|Hard|
+|[N-Queens](https://oj.leetcode.com/problems/n-queens/)| [C++](./src/nQueens/nQueuens.cpp)|2012/3/19|Hard|
+|["Pow(x, n)"](https://oj.leetcode.com/problems/powx-n/)| [C++](./src/pow/pow.cpp)|2012/3/19|Medium|
+|[Anagrams](https://oj.leetcode.com/problems/anagrams/)| [C++](./src/anagrams/anagrams.cpp)|2012/3/19|Medium|
+|[Rotate Image](https://oj.leetcode.com/problems/rotate-image/)| [C++](./src/rotateImage/rotateImage.cpp)|2012/3/17|Medium|
+|[Permutations II](https://oj.leetcode.com/problems/permutations-ii/)| [C++](./src/permutations/permutations.II.cpp)|2012/3/16|Hard|
+|[Permutations](https://oj.leetcode.com/problems/permutations/)| [C++](./src/permutations/permutations.cpp)|2012/3/16|Medium|
+|[Jump Game II](https://oj.leetcode.com/problems/jump-game-ii/)| [C++](./src/jumpGame/jumpGame.II.cpp)|2012/3/16|Hard|
+|[Wildcard Matching](https://oj.leetcode.com/problems/wildcard-matching/)| [C++](./src/wildcardMatching/wildcardMatching.cpp)|2012/3/15|Hard|
+|[Multiply Strings](https://oj.leetcode.com/problems/multiply-strings/)| [C++](./src/multiplyStrings/multiplyStrings.cpp)|2012/3/12|Medium|
+|[Trapping Rain Water](https://oj.leetcode.com/problems/trapping-rain-water/)| [C++](./src/trappingRainWater/trappingRainWater.cpp)|2012/3/10|Hard|
+|[First Missing Positive](https://oj.leetcode.com/problems/first-missing-positive/)| [C++](./src/firstMissingPositive/firstMissingPositive.cpp)|2012/3/8|Hard|
+|[Combination Sum II](https://oj.leetcode.com/problems/combination-sum-ii/)| [C++](./src/combinationSum/combinationSum.II.cpp)|2012/3/6|Medium|
+|[Combination Sum](https://oj.leetcode.com/problems/combination-sum/)| [C++](./src/combinationSum/combinationSum.cpp)|2012/3/6|Medium|
+|[Count and Say](https://oj.leetcode.com/problems/count-and-say/)| [C++](./src/countAndSay/countAndSay.cpp)|2012/3/5|Easy|
+|[Sudoku Solver](https://oj.leetcode.com/problems/sudoku-solver/)| [C++](./src/sudokuSolver/sudokuSolver.cpp)|2012/3/4|Hard|
+|[Valid Sudoku](https://oj.leetcode.com/problems/valid-sudoku/)| [C++](./src/validSudoku/validSudoku.cpp)|2012/3/3|Easy|
+|[Search Insert Position](https://oj.leetcode.com/problems/search-insert-position/)| [C++](./src/searchInsertPosition/searchInsertPosition.cpp)|2012/3/3|Medium|
+|[Search for a Range](https://oj.leetcode.com/problems/search-for-a-range/)| [C++](./src/searchForRange/searchForRange.cpp)|2012/3/2|Medium|
+|[Search in Rotated Sorted Array](https://oj.leetcode.com/problems/search-in-rotated-sorted-array/)| [C++](./src/searchInRotatedSortedArray/searchInRotatedSortedArray.cpp)|2012/3/2|Hard|
+|[Longest Valid Parentheses](https://oj.leetcode.com/problems/longest-valid-parentheses/)| [C++](./src/longestValidParentheses/longestValidParentheses.cpp)|2012/2/29|Hard|
+|[Next Permutation](https://oj.leetcode.com/problems/next-permutation/)| [C++](./src/nextPermutation/nextPermutation.cpp)|2012/2/25|Medium|
+|[Substring with Concatenation of All Words](https://oj.leetcode.com/problems/substring-with-concatenation-of-all-words/)| [C++](./src/substringWithConcatenationOfAllWords/substringWithConcatenationOfAllWords.cpp)|2012/2/23|Hard|
+|[Divide Two Integers](https://oj.leetcode.com/problems/divide-two-integers/)| [C++](./src/divideTwoInt/divideTwoInt.cpp)|2012/2/18|Medium|
+|[Implement strStr()](https://oj.leetcode.com/problems/implement-strstr/)| [C++](./src/strStr/strStr.cpp)|2012/2/18|Easy|
+|[Remove Element](https://oj.leetcode.com/problems/remove-element/)| [C++](./src/removeElement/removeElement.cpp)|2012/2/16|Easy|
+|[Remove Duplicates from Sorted Array](https://oj.leetcode.com/problems/remove-duplicates-from-sorted-array/)| [C++](./src/removeDuplicatesFromSortedArray/removeDuplicatesFromSortedArray.cpp)|2012/2/16|Easy|
+|[Reverse Nodes in k-Group](https://oj.leetcode.com/problems/reverse-nodes-in-k-group/)| [C++](./src/reverseNodesInKGroup/reverseNodesInKGroup.cpp)|2012/2/15|Hard|
+|[Swap Nodes in Pairs](https://oj.leetcode.com/problems/swap-nodes-in-pairs/)| [C++](./src/swapNodesInPairs/swapNodesInPairs.cpp)|2012/2/14|Medium|
+|[Merge k Sorted Lists](https://oj.leetcode.com/problems/merge-k-sorted-lists/)| [C++](./src/mergeKSortedLists/mergeKSortedLists.cpp)|2012/2/13|Hard|
+|[Generate Parentheses](https://oj.leetcode.com/problems/generate-parentheses/)| [C++](./src/generateParentheses/generateParentheses.cpp)|2012/2/12|Medium|
+|[Valid Parentheses](https://oj.leetcode.com/problems/valid-parentheses/)| [C++](./src/validParentheses/validParentheses.cpp)|2012/1/30|Easy|
+|[Remove Nth Node From End of List](https://oj.leetcode.com/problems/remove-nth-node-from-end-of-list/)| [C++](./src/removeNthNodeFromEndOfList/removeNthNodeFromEndOfList.cpp)|2012/1/27|Easy|
+|[Letter Combinations of a Phone Number](https://oj.leetcode.com/problems/letter-combinations-of-a-phone-number/)| [C++](./src/letterCombinationsOfAPhoneNumber/letterCombinationsOfAPhoneNumber.cpp)|2012/1/26|Medium|
+|[4Sum](https://oj.leetcode.com/problems/4sum/)| [C++](./src/4Sum/4Sum.cpp)|2012/1/26|Medium|
+|[3Sum Closest](https://oj.leetcode.com/problems/3sum-closest/)| [C++](./src/3SumClosest/3SumClosest.cpp)|2012/1/18|Medium|
+|[3Sum](https://oj.leetcode.com/problems/3sum/)| [C++](./src/3Sum/3Sum.cpp)|2012/1/17|Medium|
+|[Longest Common Prefix](https://oj.leetcode.com/problems/longest-common-prefix/)| [C++](./src/longestCommonPrefix/longestCommonPrefix.cpp)|2012/1/17|Easy|
+|[Roman to Integer](https://oj.leetcode.com/problems/roman-to-integer/)| [C++](./src/romanToInteger/romanToInteger.cpp)|2012/1/15|Easy|
+|[Integer to Roman](https://oj.leetcode.com/problems/integer-to-roman/)| [C++](./src/integerToRoman/integerToRoman.cpp)|2012/1/15|Medium|
+|[Container With Most Water](https://oj.leetcode.com/problems/container-with-most-water/)| [C++](./src/containerWithMostWater/containerWithMostWater.cpp)|2012/1/8|Medium|
+|[Regular Expression Matching](https://oj.leetcode.com/problems/regular-expression-matching/)| [C++](./src/regularExpressionMatching/regularExpressionMatching.cpp)|2012/1/8|Hard|
+|[Palindrome Number](https://oj.leetcode.com/problems/palindrome-number/)| [C++](./src/palindromeNumber/palindromeNumber.cpp)|2012/1/4|Easy|
+|[String to Integer (atoi)](https://oj.leetcode.com/problems/string-to-integer-atoi/)| [C++](./src/stringToIntegerAtoi/stringToIntegerAtoi.cpp)|2011/12/26|Easy|
+|[Reverse Integer](https://oj.leetcode.com/problems/reverse-integer/)| [C++](./src/reverseInteger/reverseInteger.cpp)|2011/12/25|Easy|
+|[ZigZag Conversion](https://oj.leetcode.com/problems/zigzag-conversion/)| [C++](./src/zigZagConversion/zigZagConversion.cpp)|2011/12/5|Easy|
+|[Longest Palindromic Substring](https://oj.leetcode.com/problems/longest-palindromic-substring/)| [C++](./src/longestPalindromicSubstring/longestPalindromicSubstring.cpp)|2011/11/11|Medium|
+|[Add Two Numbers](https://oj.leetcode.com/problems/add-two-numbers/)| [C++](./src/addTwoNumbers/addTwoNumbers.cpp)|2011/11/1|Medium|
+|[Longest Substring Without Repeating Characters](https://oj.leetcode.com/problems/longest-substring-without-repeating-characters/)| [C++](./src/longestSubstringWithoutRepeatingCharacters/longestSubstringWithoutRepeatingCharacters.cpp)|2011/5/15|Medium|
+|[Median of Two Sorted Arrays](https://oj.leetcode.com/problems/median-of-two-sorted-arrays/)| [C++](./src/medianOfTwoSortedArrays/medianOfTwoSortedArrays.cpp)|2011/3/27|Hard|
+|[Two Sum](https://oj.leetcode.com/problems/two-sum/)| [C++](./src/twoSum/twoSum.cpp)|2011/3/13|Medium|
diff --git a/src2/2Sum/2sum.py b/src2/2Sum/2sum.py
new file mode 100644
index 000000000..35552b3b2
--- /dev/null
+++ b/src2/2Sum/2sum.py
@@ -0,0 +1,32 @@
+'''
+Given an array of integers, find two numbers such that they add up to a specific target number.
+
+The function twoSum should return indices of the two numbers such that they add up to the target, 
+
+where index1 must be less than index2. Please note that your returned answers (both index1 and index2) are not zero-based.
+
+You may assume that each input would have exactly one solution.
+
+Input: numbers={2, 7, 11, 15}, target=9
+Output: index1=1, index2=2
+'''
+
+
+class Solution:
+    # @return a tuple, (index1, index2)
+    def twoSum(self, num, target):
+    	match = dict()
+
+    	for i in range(len(num)):
+    		v = match.get(num[i], None)
+    		if v != None:
+    			return v + 1, i + 1
+
+    		match[target - num[i]] = i
+
+    	return None
+
+if __name__ == '__main__':
+	s = Solution();
+	print s.twoSum([3,2,4], 6)
+        
\ No newline at end of file
diff --git a/src2/3Sum/3Sum.py b/src2/3Sum/3Sum.py
new file mode 100644
index 000000000..646b7e4d6
--- /dev/null
+++ b/src2/3Sum/3Sum.py
@@ -0,0 +1,65 @@
+
+'''
+Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? 
+Find all unique triplets in the array which gives the sum of zero.
+
+Note:
+Elements in a triplet (a,b,c) must be in non-descending order. (ie, a <= b <= c)
+
+The solution set must not contain duplicate triplets.
+    For example, given array S = {-1 0 1 2 -1 -4},
+
+    A solution set is:
+    (-1, 0, 1)
+    (-1, -1, 2)
+
+'''
+def binary_search(array, value):
+	low, high = 0, len(array)
+	while low < high:
+		mid = (low + high) / 2
+		midval = array[mid]
+		if midval < value:
+			low = mid+1
+		elif midval > value:
+			high = mid
+		else:
+			return mid
+
+	return None
+
+class Solution:
+    # @return a list of lists of length 3, [[val1,val2,val3]]\
+    def threeSum(self, num):
+    	mapping = []
+    	num.sort()
+    	numLen = len(num)
+
+    	# i step forward
+    	for i in range(numLen):
+    		if num[i] > 0 or (num[i] == num[i-1] and i != 0):
+    			continue
+
+			# j step backward
+    		for j in reversed(range(i + 1, numLen)):
+    			if j + 1 != numLen and num[j] == num[j+1]:
+    				continue
+
+    			needed = 0-num[i]-num[j]
+    			if needed < num[i]:
+    				continue
+    			if needed > num[j]:
+    				break 
+    				
+    			# binary_search is better for find middle value
+    			if binary_search(num[i+1:j], needed) != None: 
+    				mapping.append([num[i], needed, num[j]])
+
+        return mapping
+
+
+if __name__ == '__main__':
+	rst = Solution().threeSum([-2, -1, 0, 1, 2, 3])
+	rst.sort()
+	print rst
+	print Solution().threeSum([])
diff --git a/src2/4Sum/4Sum.py b/src2/4Sum/4Sum.py
new file mode 100644
index 000000000..be38f6737
--- /dev/null
+++ b/src2/4Sum/4Sum.py
@@ -0,0 +1,74 @@
+'''
+
+Given an array S of n integers, are there elements a, b, c, and d in S such that a + b + c + d = target?
+Find all unique quadruplets in the array which gives the sum of target.
+
+Note:
+Elements in a quadruplet (a,b,c,d) must be in non-descending order. (ie, a <= b <= c <= d)
+The solution set must not contain duplicate quadruplets.
+
+ For example, given array S = {1 0 -1 0 -2 2}, and target = 0.
+
+    A solution set is:
+    (-1,  0, 0, 1)
+    (-2, -1, 1, 2)
+    (-2,  0, 0, 2)
+'''
+
+def binary_search(array, value):
+	low, high = 0, len(array)
+	while low < high:
+		mid = (low + high) / 2
+		midval = array[mid]
+		if midval < value:
+			low = mid+1
+		elif midval > value:
+			high = mid
+		else:
+			return mid
+
+	return None
+
+class Solution:
+	# @return a list of lists of length 4, [[val1,val2,val3,val4]]
+	def fourSum(self, num, target):
+		mapping = []
+		num.sort()
+		itemNum = len(num)
+		for s in range(0, itemNum - 3):
+			if s != 0 and num[s] == num[s-1]:
+				continue
+
+			for e in reversed(range(s + 3, itemNum)):
+				if e != itemNum-1 and num[e] == num[e+1]:
+					continue
+
+				sumSE = num[s] + num[e]
+				neededBySE = target - sumSE
+
+				if neededBySE < num[s+1]*2 or num[e-1]*2 < neededBySE:
+					continue
+
+				for s2 in range(s + 1, e - 1):
+					if s2 != s+1 and num[s2] == num[s2-1]:
+						continue
+
+					needed = neededBySE - num[s2]
+					if needed < num[s2 + 1]:
+						continue
+					if not binary_search(num[s2+1:e], needed) is None:
+						mapping.append([num[s], num[s2], needed, num[e]])
+		return mapping
+
+if __name__ == '__main__':
+	#print Solution().fourSum([1, 0, -1, 0, -2, 2], 0)
+	#print Solution().fourSum([0,0], 0)
+	print Solution().fourSum([-1,2,2,-5,0,-1,4], 3)
+	a = "123455"
+	if a afs
+		sadfasdf
+
+
+
+
+
diff --git a/src2/AddTwoNumbers/add_two_numbers.py b/src2/AddTwoNumbers/add_two_numbers.py
new file mode 100644
index 000000000..c8e9d11ce
--- /dev/null
+++ b/src2/AddTwoNumbers/add_two_numbers.py
@@ -0,0 +1,112 @@
+'''
+You are given two linked lists representing two non-negative numbers. 
+The digits are stored in reverse order and each of their nodes contain a single digit. 
+Add the two numbers and return it as a linked list.
+
+Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
+Output: 7 -> 0 -> 8
+342 + 465 = 807
+'''
+
+class ListNode:
+    def __init__(self, x):
+        self.val = x
+        self.next = None
+
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+# optimize cause too much code.
+
+class Solution:
+
+    # @return carry, result
+    def splitSum(self, s):
+        if s >= 10:
+            return 1, s-10 
+        else:
+            return 0, s
+
+    # @return new node
+    def addValue(self, node, sum):
+        node.next = ListNode(sum)
+        return node.next
+
+    # @return a ListNode
+    def addTwoNumbers(self, l1, l2):
+        if l1 == None and l2 == None:
+            return None
+
+        headValue = 0
+        if l1 != None:
+            headValue += l1.val
+            l1 = l1.next
+
+        if l2 != None:
+            headValue += l2.val
+            l2 = l2.next
+
+        carry, headValue = self.splitSum(headValue)
+        result = head = ListNode(headValue)
+
+        while l1 != None and l2 != None:
+            carry, sum = self.splitSum(l1.val + l2.val + carry)
+            result = self.addValue(result, sum)
+
+            l1 = l1.next
+            l2 = l2.next
+
+        while l1 != None:
+            carry, sum = self.splitSum(l1.val + carry)
+            result = self.addValue(result, sum)
+            l1 = l1.next
+
+        while l2 != None:
+            carry, sum = self.splitSum(l2.val + carry)
+            result = self.addValue(result, sum)
+            l2 = l2.next
+
+        if carry == 1:
+            result = self.addValue(result, 1)
+        return head
+
+    def makeList(self, src):
+        if src == None:
+            return None
+
+        p = head = ListNode(src[0])
+        for i in range(1, len(src)):
+            p = self.addValue(p, src[i])
+        return head
+
+makeList =  Solution().makeList
+
+def show(l):
+    p = l
+    while p != None:
+        print p.val
+        p = p.next
+
+def list2Array(l):
+    r = list()
+    while l != None:
+        r.append(l.val)
+        l = l.next
+    return r
+
+def test(l1, l2, expect):
+    result = Solution().addTwoNumbers(makeList(l1), makeList(l2))
+    result = list2Array(result)
+    if expect != result:
+        print "l1:", l1
+        print "l2:", l2
+        print "expect:", expect
+        print "result:", result
+
+if __name__ == '__main__':
+    test([2, 4, 3], [5, 6, 4], [7, 0, 8])
+    test([2, 4, 3], [5, 6, 4, 1], [7, 0, 8, 1])
+    test([2, 4, 3, 1], [5, 6, 4], [7, 0, 8, 1])
+
diff --git a/src2/BinaryTreeRightSideView/binary_tree_right_side_view.py b/src2/BinaryTreeRightSideView/binary_tree_right_side_view.py
new file mode 100644
index 000000000..210515113
--- /dev/null
+++ b/src2/BinaryTreeRightSideView/binary_tree_right_side_view.py
@@ -0,0 +1,49 @@
+import sys
+sys.path.append('../../test_framework')
+#from test_framework.binary_tree import *
+from test_framework import *
+
+# Definition for a  binary tree node
+# class TreeNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.left = None
+#         self.right = None
+
+class Solution:
+    # @param root, a tree node
+    # @return a list of integers
+    def rightSideView(self, root):
+        stack = []
+        p = root
+        result = []
+        currentLevel = 0
+
+        while p != None:
+            # p is a most right node never traversed.
+            if currentLevel == len(result):
+                result.append(p.val)
+
+            if p.right != None:
+                stack.append(p)
+                p = p.right
+                currentLevel += 1
+            elif p.left != None:
+                stack.append(p)
+                p = p.left
+                currentLevel += 1
+            else:
+                while stack
+                parent = stack[-1]
+                while p == parent.left:
+                    p = parent
+                    currentLevel -= 1
+                    stack.pop()
+                    parent = stack[-1]
+                p = parent.left
+        return result
+
+
+if __name__ == '__main__':
+    root = binary_tree.BinaryTree().build([1])
+    Solution().rightSideView(root)
\ No newline at end of file
diff --git a/src2/CountPrimes/count_primes.js b/src2/CountPrimes/count_primes.js
new file mode 100644
index 000000000..efa35aba0
--- /dev/null
+++ b/src2/CountPrimes/count_primes.js
@@ -0,0 +1,35 @@
+"use strict"
+/**
+ * @param {number} n
+ * @return {number}
+ */
+function show(n){
+	console.log(n);
+}
+
+var countPrimes = function(n) {
+	var scanned = new Int8Array(n);
+	for (var i = 2; i < n; i++){
+		if (!scanned[i]){
+			for (var j = i * i; j < n; j+=i){
+				scanned[j] = true;
+			}
+		}
+	}
+	show(scanned);
+
+	var count = 0;
+	for (var k = 2; k < n; i++){
+		if (!scanned[k]){
+			count++;
+		}
+	}
+	return count;
+};
+
+
+show(countPrimes(1));
+show(countPrimes(3));
+show(countPrimes(10));
+// show(countPrimes(25));
+show(countPrimes(1000));
\ No newline at end of file
diff --git a/src2/CountPrimes/count_primes.py b/src2/CountPrimes/count_primes.py
new file mode 100644
index 000000000..e2b6af81b
--- /dev/null
+++ b/src2/CountPrimes/count_primes.py
@@ -0,0 +1,14 @@
+class Solution:
+    # @param {integer} n
+    # @return {integer}
+    def countPrimes(self, n):
+        scanned = [True] * (max(n+1, 2))
+        scanned[0] = scanned[1] = False
+        for i in range(2, n+1):
+            if scanned[i]:
+                for j in range(i*i, n+1, i):
+                    scanned[j] = False
+        return scanned.count(True)
+
+if __name__ == '__main__':
+    print Solution().countPrimes(10)
\ No newline at end of file
diff --git a/src2/FlattenNestedListIterator/flatten_nested_list_iterator.py b/src2/FlattenNestedListIterator/flatten_nested_list_iterator.py
new file mode 100644
index 000000000..636e955de
--- /dev/null
+++ b/src2/FlattenNestedListIterator/flatten_nested_list_iterator.py
@@ -0,0 +1,49 @@
+# """
+# This is the interface that allows for creating nested lists.
+# You should not implement it, or speculate about its implementation
+# """
+#class NestedInteger(object):
+#    def isInteger(self):
+#        """
+#        @return True if this NestedInteger holds a single integer, rather than a nested list.
+#        :rtype bool
+#        """
+#
+#    def getInteger(self):
+#        """
+#        @return the single integer that this NestedInteger holds, if it holds a single integer
+#        Return None if this NestedInteger holds a nested list
+#        :rtype int
+#        """
+#
+#    def getList(self):
+#        """
+#        @return the nested list that this NestedInteger holds, if it holds a nested list
+#        Return None if this NestedInteger holds a single integer
+#        :rtype List[NestedInteger]
+#        """
+
+class NestedIterator(object):
+
+    def __init__(self, nestedList):
+        """
+        Initialize your data structure here.
+        :type nestedList: List[NestedInteger]
+        """
+        
+
+    def next(self):
+        """
+        :rtype: int
+        """
+        
+
+    def hasNext(self):
+        """
+        :rtype: bool
+        """
+        
+
+# Your NestedIterator object will be instantiated and called as such:
+# i, v = NestedIterator(nestedList), []
+# while i.hasNext(): v.append(i.next())
\ No newline at end of file
diff --git a/src2/HappyNumber/happy_number.py b/src2/HappyNumber/happy_number.py
new file mode 100644
index 000000000..6915fe3a5
--- /dev/null
+++ b/src2/HappyNumber/happy_number.py
@@ -0,0 +1,18 @@
+class Solution:
+    # @param {integer} n
+    # @return {boolean}
+    def isHappy(self, n):
+        loop = set([n])
+        while n != 1:
+            m = str(n)
+            temp = reduce(lambda x,y: x + y, map(lambda x: int(x)*int(x), m))
+            if (temp in loop):
+                return False
+            else:
+                loop.add(temp)
+                n = temp
+        return True
+
+if __name__ == '__main__':
+    print Solution().isHappy(2);
+    # print reduce(lambda x,y: int(x)*int(x) + int(y)*int(y), "82")
\ No newline at end of file
diff --git a/src2/MediaOfTwoSortedArrays/MediaOfTwoSortedArrayst.py b/src2/MediaOfTwoSortedArrays/MediaOfTwoSortedArrayst.py
new file mode 100644
index 000000000..8d8e71e0f
--- /dev/null
+++ b/src2/MediaOfTwoSortedArrays/MediaOfTwoSortedArrayst.py
@@ -0,0 +1,80 @@
+'''
+There are two sorted arrays A and B of size m and n respectively. 
+
+Find the median of the two sorted arrays. 
+
+The overall run time complexity should be O(log (m+n)).
+'''
+
+class Solution:
+    # get media of A --> ma
+    # get count of number in B that smaller than ma
+    def getNumBiggerThanValue(self, Array, Value):
+        # lower bounder is better
+        for i in range(len(Array)):
+            if Array[i] > Value:
+                return i + 1
+        return len(Array)
+
+    # return iA, iB
+    def moveFoward(self, A, B, iA, iB):
+        # min of A[iA + 1], B[iB]
+        if iB == len(B):
+            return iA + 1, iB
+        elif iA == len(A):
+            return iB + 1, iA
+        else
+
+    # @return a float
+    def findMedianSortedArrays(self, A, B):
+        lenA = len(A)
+        lenB = len(B)
+        mid = (lenA + lenB) / 2
+        if lenA >= lenB:
+            iA = len(A) / 2
+            iB = self.getNumBiggerThanValue(B, A[iA])
+        else:
+            iB = len(B) / 2
+            iA = self.getNumBiggerThanValue(A, B[iB])
+        A.append(0x8ffffffff)
+        B.append(0x8ffffffff)
+
+        while True:
+            ## step
+            left = iA + iB
+            #print mid, left, iA, iB, ".."
+            if left == mid:
+                return min(A[iA], B[iB])
+            elif left < mid:
+                # step forward
+                if A[iA - 1] > B[iB - 1]:
+                    iB+=1
+                else:
+                    iA+=1
+            elif left > mid:
+                # step backward
+                if A[iA] > B[iB]:
+                    iA-=1
+                else:
+                    iB-=1
+            #print "A:%d, B:%d" %(A[iA], B[iB])
+            
+
+if __name__ == '__main__':
+    slu = Solution()
+    print slu.findMedianSortedArrays([1], [2])
+    print slu.findMedianSortedArrays([1, 12, 15, 26, 38], [2, 13, 17, 30, 45, 50])
+    print slu.findMedianSortedArrays([1, 12, 15, 26, 38], [2, 13, 17, 30, 45])
+    print slu.findMedianSortedArrays([1, 2, 5, 6, 8], [13, 17, 30, 45, 50])
+    print slu.findMedianSortedArrays([1, 2, 5, 6, 8, 9, 10], [13, 17, 30, 45, 50])
+    print slu.findMedianSortedArrays([1, 2, 5, 6, 8, 9], [13, 17, 30, 45, 50])
+    print slu.findMedianSortedArrays([1, 2, 5, 6, 8], [11, 13, 17, 30, 45, 50])
+    print slu.findMedianSortedArrays([1], [2,3,4])
+    ## [1,2,3] --> 2
+    ## [1,2,3,4] --> 3
+    ## [1,2,4,5,5,8] ==> 5
+    ## [1,2,4,5,5,6,8] ==> 5
+        
+
+
+            
diff --git a/src2/MinStack/MinStack.py b/src2/MinStack/MinStack.py
new file mode 100644
index 000000000..f410eaf9a
--- /dev/null
+++ b/src2/MinStack/MinStack.py
@@ -0,0 +1,39 @@
+'''
+Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.
+
+push(x) -- Push element x onto stack.
+pop() -- Removes the element on top of the stack.
+top() -- Get the top element.
+getMin() -- Retrieve the minimum element in the stack.
+'''
+class MinStack:
+    # @param x, an integer
+    # @return an integer
+    def __init__(self):
+        self.m_nums = list()
+        self.m_minValue = 0x8fffffff
+        self.m_minIndex = 0
+
+    def push(self, x):
+        self.m_nums.append(x)
+        if self.m_minValue > x:
+            self.m_minValue, self.m_minIndex = x, len(self.m_nums)
+
+    # @return nothing
+    def pop(self):
+        if self.m_minIndex == len(self.m_nums):
+            self.m_minValue = min(self.m_nums)
+            self.m_minIndex = self.m_nums.index(self.m_minValue)
+
+        self.m_nums.pop()
+
+    # @return an integer
+    def top(self):
+    	if len(self.m_nums) == 0:
+    		return None
+        return self.m_nums[0]
+
+    # @return an integer
+    def getMin(self):
+        return self.m_minValue
+        #return min(self.m_nums)
\ No newline at end of file
diff --git a/src2/NumberOf1Bits/number_of_1_bits.py b/src2/NumberOf1Bits/number_of_1_bits.py
new file mode 100644
index 000000000..b82694238
--- /dev/null
+++ b/src2/NumberOf1Bits/number_of_1_bits.py
@@ -0,0 +1,21 @@
+'''
+Write a function that takes an unsigned integer and 
+
+returns the number of '1' bits it has (also known as the Hamming weight).
+
+For example, the 32-bit integer '11' has binary representation
+
+00000000000000000000000000001011, so the function should return 3.
+'''
+
+class Solution:
+    # @param n, an integer
+    # @return an integer
+    def hammingWeight(self, n):
+        p = 0
+        for i in range(32):
+            p += (n >> i) & 1
+        return p
+
+if __name__ == '__main__':
+    print Solution().hammingWeight(11)
\ No newline at end of file
diff --git a/src2/NumberOf1Bits/number_of_1_bits.rb b/src2/NumberOf1Bits/number_of_1_bits.rb
new file mode 100644
index 000000000..6c0b25e36
--- /dev/null
+++ b/src2/NumberOf1Bits/number_of_1_bits.rb
@@ -0,0 +1,16 @@
+"
+Write a function that takes an unsigned integer and 
+
+returns the number of ’1' bits it has (also known as the Hamming weight).
+
+For example, the 32-bit integer ’11' has binary representation 
+
+00000000000000000000000000001011, so the function should return 3.
+
+"
+
+# @param {Integer} n, a positive integer
+# @return {Integer}
+def hamming_weight(n)
+    [0..32].each x | puts(x)
+end
\ No newline at end of file
diff --git a/src2/NumberOfIsland/number_of_island.py b/src2/NumberOfIsland/number_of_island.py
new file mode 100644
index 000000000..e457242e7
--- /dev/null
+++ b/src2/NumberOfIsland/number_of_island.py
@@ -0,0 +1,34 @@
+class Solution:
+
+    def traverseIsland(self, grid, col, line):
+        if (line < 0 or self.lineNum <= line or col < 0 or self.colNum <= col or grid[line][col] == '0'):
+            return
+
+        grid[line][col] = '0'
+        self.traverseIsland(grid, col, line + 1)
+        self.traverseIsland(grid, col, line - 1)
+        self.traverseIsland(grid, col + 1, line)
+        self.traverseIsland(grid, col - 1, line)
+
+    # @param grid, a list of list of characters
+    # @return an integer
+    def numIslands(self, grid):
+        islandNum = 0
+        self.lineNum = len(grid)
+        if (self.lineNum == 0):
+            return 0
+        self.colNum = len(grid[0])
+
+        for j in range(self.lineNum):
+            grid[j] = list(grid[j])
+
+        for j in range(self.lineNum):
+            line = grid[j]
+            for i in range(self.colNum):
+                if (line[i] == '1'):
+                    islandNum += 1
+                    self.traverseIsland(grid, i, j)
+        return islandNum
+
+if __name__ == '__main__':
+    print Solution().numIslands(["1011"])
\ No newline at end of file
diff --git a/src2/RemoveLinkedListElements/remove_linked_list_elements.py b/src2/RemoveLinkedListElements/remove_linked_list_elements.py
new file mode 100644
index 000000000..406b067d9
--- /dev/null
+++ b/src2/RemoveLinkedListElements/remove_linked_list_elements.py
@@ -0,0 +1,33 @@
+import sys
+sys.path.append('../../test_framework')
+from test_framework import *
+
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+class Solution:
+    # @param {ListNode} head
+    # @param {integer} val
+    # @return {ListNode}
+    def removeElements(self, head, val):
+        p = head;
+        while p != None:
+            pNext = p.next;
+            while pNext != None and pNext.val == val:
+                pNext = pNext.next
+            p.next = pNext
+            p = pNext
+        if head.val == val:
+            head = head.next
+        return head;
+
+
+if __name__ == '__main__':
+    # head = makeList([1,2,3,4])
+    # Solution().removeElements(head, 3).show()
+
+    head = makeList([3,3,1])
+    Solution().removeElements(head, 3).show()
diff --git a/src2/ReverseInteger/ReverseInteger.py b/src2/ReverseInteger/ReverseInteger.py
new file mode 100644
index 000000000..5df5ef05f
--- /dev/null
+++ b/src2/ReverseInteger/ReverseInteger.py
@@ -0,0 +1,24 @@
+class Solution:
+    # @return an integer
+    def reverse(self, x):
+    	strX = str(x)
+    	#strX = list(strX)
+    	prefix = ''
+    	if strX[0] == '-':
+    		strX = strX[1:]
+    		prefix = '-'
+
+    	strX = list(strX)
+    	strX.reverse()
+    	strX = prefix + ''.join(strX)
+    	x = int(strX)
+    	if x > 2147483647:
+    		return 0
+    	if x < -2147483648:
+    		return 0
+    	return x
+     
+
+if __name__ == '__main__':
+	print Solution().reverse(2147483647)
+	print Solution().reverse(0)
\ No newline at end of file
diff --git a/src2/SortList/sort_list.py b/src2/SortList/sort_list.py
new file mode 100644
index 000000000..15ea277e3
--- /dev/null
+++ b/src2/SortList/sort_list.py
@@ -0,0 +1,46 @@
+'''
+Sort a linked list in O(n log n) time using constant space complexity.
+'''
+
+import sys
+sys.path.append('../../test_framework')
+from test_framework import *
+
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+class Solution:
+    # @param head, a ListNode
+    # @return a ListNode
+    def quickSortList(self, head):
+        middle = head
+        l = r = None
+
+        p = head.next
+        lp = rp = middle
+        
+        while p != None:
+            pNext = p.next
+            if p.val >= middle.val:
+                p.next = lp
+                lp = p
+            else:
+                rp.next = p
+                rp = p
+            p = pNext
+
+        rp.next = None
+        return lp
+
+    def sortList(self, head):
+        # p = head
+        head = self.quickSortList(head)
+        head.show()
+
+if __name__ == '__main__':
+    head = makeList([5, 4, 5, 3, 7])
+    # head.show()
+    Solution().sortList(head)
\ No newline at end of file
diff --git a/src2/WordBreak/word_break.py b/src2/WordBreak/word_break.py
new file mode 100644
index 000000000..06fd33ca0
--- /dev/null
+++ b/src2/WordBreak/word_break.py
@@ -0,0 +1,47 @@
+'''
+Given a string s and a dictionary of words dict, 
+determine if s can be segmented into a space-separated sequence of one or more dictionary words.
+
+For example, given
+s = "leetcode",
+dict = ["leet", "code"].
+
+Return true because "leetcode" can be segmented as "leet code".
+'''
+
+class Solution:
+    # @param s, a string
+    # @param dict, a set of string
+    # @return a boolean
+    def wordBreak_old(self, s, dict):
+        if s in dict:
+            return True
+        print "----------------"
+        for i in range(1, len(s)):
+            print s[:i], ":|:", s[i:]
+            if self.wordBreak(s[:i], dict) and self.wordBreak(s[i:], dict):
+                return True
+        return False
+
+    def wordBreak(self, s, dict):
+        sLen = len(s)
+        charsInDict = [False] * (sLen)
+
+        for i in range(0, sLen):
+            charsInDict[i] = s[:i+1] in dict
+            if charsInDict[i] is True:
+                continue
+
+            for j in range(0, i):
+                charsInDict[i] = charsInDict[j] is True and s[j+1:i+1] in dict
+        return charsInDict[sLen-1]
+
+if __name__ == '__main__':
+    print Solution().wordBreak("leetcode", dict = ["leet", "code"])
+    print Solution().wordBreak("goalspecial", dict = ["go","goal","goals","special"])
+    print Solution().wordBreak("bccdbacdbdacddabbaaaadababadad", \
+        ["cbc","bcda","adb","ddca","bad","bbb","dad","dac","ba","aa","bd",\
+        "abab","bb","dbda","cb","caccc","d","dd","aadb","cc","b","bcc","bcd",\
+        "cd","cbca","bbd","ddd","dabb","ab","acd","a","bbcc","cdcbd","cada",\
+        "dbca","ac","abacd","cba","cdb","dbac","aada","cdcda","cdc","dbc","dbcb",\
+        "bdb","ddbdd","cadaa","ddbc","babb"])
\ No newline at end of file
diff --git a/test_framework/__init__.py b/test_framework/__init__.py
new file mode 100644
index 000000000..1fae5c3ef
--- /dev/null
+++ b/test_framework/__init__.py
@@ -0,0 +1 @@
+__all__ = ["binary_tree", "single_list"]
diff --git a/test_framework/binary_tree.py b/test_framework/binary_tree.py
new file mode 100644
index 000000000..cde64294d
--- /dev/null
+++ b/test_framework/binary_tree.py
@@ -0,0 +1,50 @@
+
+class BinaryTree:
+    def __init__(self, val = None):
+        self.val = val
+        self.left = None
+        self.right = None
+
+    def setChild(self, leftValue, rightValue):
+        if (leftValue != None):
+            self.left = BinaryTree(leftValue)
+        if (rightValue != None):
+            self.right = BinaryTree(rightValue)
+
+    def build(self, data):
+        if len(data) == 0:
+            return None
+        root = BinaryTree(data[0])
+        openNode = [root]
+        for i in range(1, len(data), 2):
+            node = openNode.pop()
+            if i + 1 == len(data):
+                node.setChild(data[i], None)
+            else:
+                node.setChild(data[i], data[i+1])
+            openNode.append([node.left, node.right])
+        return root
+
+    def show(self):
+        layer = [self]
+        p = self
+        level = 0
+        while len(layer) != 0:
+            values = []
+            nextLayer = []
+            for node in layer:
+                if node == None:
+                    values.append("#")
+                else:
+                    values.append(node.val)
+                    nextLayer.append(node.left)
+                    nextLayer.append(node.right)
+
+            print "level: %d, data:" % (level),
+            print values
+            layer = nextLayer
+            level += 1
+
+if __name__ == '__main__':
+    root = BinaryTree().build([1,2,3])
+    root.show()
diff --git a/test_framework/single_list.py b/test_framework/single_list.py
new file mode 100644
index 000000000..20fa61cb9
--- /dev/null
+++ b/test_framework/single_list.py
@@ -0,0 +1,42 @@
+
+class ListNode:
+    def __init__(self, x):
+        self.val = x
+        self.next = None
+
+    # @return next node
+    def addNext(self, sum):
+        self.next = ListNode(sum)
+        return self.next
+
+    # @param [in] list
+    def show(self):
+        p = self
+        while p != None:
+            print p.val
+            p = p.next
+
+    def toArray(self):
+        node = self
+        r = list()
+        while node != None:
+            r.append(node.val)
+            node = node.next
+        return r
+
+# @param [in] list
+# @return header ListNode
+def makeList(array):
+    if array == None:
+        return None
+
+    p = head = ListNode(array[0])
+    for i in range(1, len(array)):
+        p = p.addNext(array[i])
+    return head
+
+def test():
+    print "this is the test of ListNode."
+
+if __name__ == '__main__':
+    test()
\ No newline at end of file