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226. Invert Binary Tree

Invert a binary tree.

     4   /     2     7 / \   / 1   3 6   9

to

     4   /     7     2 / \   / 9   6 3   1

思路:递归。用invert左子树,存在一个node,invert右子树,存在另一个node。然后左右互换即可。今天学校食堂居然没来熊猫快递,啃了个破汉堡= =。

/** * Definition for a binary tree node. * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    public TreeNode invertTree(TreeNode root) {        if(root==null)        {            return root;        }                TreeNode l1=invertTree(root.left);        TreeNode l2=invertTree(root.right);        root.right=l1;        root.left=l2;        return root;            }}

 

226. Invert Binary Tree