add 235

fishercoder1534 · fishercoder1534 · commit ac555a7d33d4 · 2017-05-13T10:41:44.000-07:00
diff --git a/README.md b/README.md
@@ -244,8 +244,8 @@ Your ideas/fixes/algorithms are more than welcome!
 |239|[Sliding Window Maximum](https://leetcode.com/problems/sliding-window-maximum/)|[Solution](../master/src/main/java/com/stevesun/solutions/SlidingWindowMaximum.java)| O(nlogn)|O(k) | Hard| Heap
 |238|[Product of Array Except Self](https://leetcode.com/problems/product-of-array-except-self/)|[Solution](../master/src/main/java/com/stevesun/solutions/ProductofArrayExceptSelf.java)| O(n)|O(1) | Medium| Array
 |237|[Delete Node in a Linked List](https://leetcode.com/problems/delete-node-in-a-linked-list/)|[Solution](../master/src/main/java/com/stevesun/solutions/_237.java)| O(1)|O(1) | Easy| LinkedList
-|235|[Lowest Common Ancestor of a Binary Tree](https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/)|[Solution](../master/src/main/java/com/stevesun/solutions/LowestCommonAncestorOfABinaryTree.java)| O(h)|O(1) | Medium| DFS
-|235|[Lowest Common Ancestor of a Binary Search Tree](https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-search-tree/)|[Solution](../master/src/main/java/com/stevesun/solutions/LowestCommonAncestorOfABinarySearchTree.java)| O(h)|O(1) | Easy| DFS
+|236|[Lowest Common Ancestor of a Binary Tree](https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-tree/)|[Solution](../master/src/main/java/com/stevesun/solutions/LowestCommonAncestorOfABinaryTree.java)| O(h)|O(1) | Medium| DFS
+|235|[Lowest Common Ancestor of a Binary Search Tree](https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-search-tree/)|[Solution](../master/src/main/java/com/stevesun/solutions/_235.java)| O(h)|O(1) | Easy| DFS
 |233|[Number of Digit One](https://leetcode.com/problems/number-of-digit-one/)|[Solution](../master/src/main/java/com/stevesun/solutions/NumberofDigitOne.java)| O(n)|O(1) | Hard| Math
 |229|[Majority Element II](https://leetcode.com/problems/majority-element-ii/)|[Solution](../master/src/main/java/com/stevesun/solutions/MajorityElementII.java)| O(n)|O(n) | Medium|
 |228|[Summary Ranges](https://leetcode.com/problems/summary-ranges/)|[Solution](../master/src/main/java/com/stevesun/solutions/SummaryRanges.java)| O(n)|O(1) | Medium| Array
diff --git a/src/main/java/com/stevesun/solutions/LowestCommonAncestorOfABinarySearchTree.java b/src/main/java/com/stevesun/solutions/LowestCommonAncestorOfABinarySearchTree.java
diff --git a/src/main/java/com/stevesun/solutions/_235.java b/src/main/java/com/stevesun/solutions/_235.java
@@ -0,0 +1,27 @@
+package com.stevesun.solutions;
+
+import com.stevesun.common.classes.TreeNode;
+
+/**Given a binary search tree (BST), find the lowest common ancestor (LCA) of two given nodes in the BST.
+
+ According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes v and w as the lowest node in T that has both v and w as descendants (where we allow a node to be a descendant of itself).”
+
+ _______6______
+ /              \
+ ___2__          ___8__
+ /      \        /      \
+ 0      _4       7       9
+ /  \
+ 3   5
+ For example, the lowest common ancestor (LCA) of nodes 2 and 8 is 6. Another example is LCA of nodes 2 and 4 is 2, since a node can be a descendant of itself according to the LCA definition.
+
+ */
+public class _235 {
+    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
+        if (root == null || p == root || q == root) return root;
+        if ((root.val - p.val) * (root.val - q.val) <= 0) return root;
+        if ((root.val - p.val) * (root.val - q.val) > 0 && (root.val - p.val) > 0) return lowestCommonAncestor(root.left, p, q);
+        if ((root.val - p.val) * (root.val - q.val) > 0 && (root.val - p.val) < 0) return lowestCommonAncestor(root.right, p, q);
+        return root;
+    }
+}
