题目
给定一个二叉树，原地将它展开为一个单链表。
例如，给定二叉树
1
/ \
2 5
/ \ \
3 4 6
将其展开为：
1
\
2
\
3
\
4
\
5
\
6
题解
/*** Definition for a binary tree node.* public class TreeNode {* int val;* TreeNode left;* TreeNode right;* TreeNode() {}* TreeNode(int val) { this.val = val; }* TreeNode(int val, TreeNode left, TreeNode right) {* this.val = val;* this.left = left;* this.right = right;* }* }*/
class Solution {TreeNode last = null;public void flatten(TreeNode root) {if(root == null) return;flatten(root.right);flatten(root.left);root.right = last;root.left = null;last = root;}
}