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Given a binary tree, flatten it to a linked list in-place.
For example,
Given
1
/ 2 5
/ \ 3 4 6
The flattened tree should look like:
1
2
3
4
5
6
前序遍历，每层都记录当前节点的左右孩子节点，用tail记录修改后的链表结尾，并返回给上一层。在修改结构之前注意把当前节点的左右置空。
1 public class FlattenBinaryTreeToLinkedList { 2 public void flatten(TreeNode root) { 3 dfs(root); 4 } 5 6 public TreeNode dfs(TreeNode root) { 7 if (root == null) { 8 return null; 9 } 10 TreeNode left = root.left; 11 TreeNode right = root.right; 12 //将当前节点的左右孩子置空 13 root.left = null; 14 root.right = null; 15 TreeNode tail = root; 16 //连接左子树 17 if (left != null) { 18 tail.right = left; 19 tail = dfs(left); 20 } 21 //连接右子树 22 if (right != null) { 23 tail.right = right; 24 tail = dfs(right); 25 } 26 return tail; 27 } 28 }
Flatten Binary Tree to Linked List
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原文地址：http://www.cnblogs.com/ivanyangzhi/p/4377120.html
