|148|[Sort List](https://leetcode.com/problems/sort-list/)|[Solution](../master/src/main/java/com/fishercoder/solutions/_148.java) O(nlogn)|O(h) | Medium| Linked List, Sort

|147|[Insertion Sort List](https://leetcode.com/problems/insertion-sort-list/)|[Solution](../master/src/main/java/com/fishercoder/solutions/InsertionSortList.java) O(n^2)|O(1) | Medium| Linked List

|146|[LRU Cache](https://leetcode.com/problems/lru-cache/)|[Doubly Linked List](../master/src/main/java/com/fishercoder/solutions/_146_use_DoublyLinkedList_plus_HashMap.java) |[Linked Hash Map](../master/leetcode-algorithms/src/main/java/com/fishercoder/solutions/_146_use_LinkedHashMap.java)| O(?)|O(?) | Hard| Linked List

|144|[Binary Tree Preorder Traversal](https://leetcode.com/problems/binary-tree-preorder-traversal/)|[Solution](../master/src/main/java/com/fishercoder/solutions/BinaryTreePreorderTraversal.java)| O(n)|O(h) | Medium| Binary Tree

|143|[Reorder List](https://leetcode.com/problems/reorder-list/)|[Solution](../master/src/main/java/com/fishercoder/solutions/ReorderList.java)| O(n)|O(1) | Medium|

|142|[Linked List Cycle II](https://leetcode.com/problems/linked-list-cycle-ii/)|[Solution](../master/src/main/java/com/fishercoder/solutions/LinkedListCycleII.java)| O(n)|O(1) | Medium| Linked List

/**A tricky one: Modify the code for pre-order traversal so that it becomes root->right->left, and then reverse the result to get left->right->root.*/

public static List<Integer> postorderTraversal_iterative(TreeNode root) {

List<Integer> result = new ArrayList();