【leetcode】226. Invert Binary Tree

题目要求：

Invert a binary tree.

     4   /   \  2     7 / \   / \1   3 6   9

to

     4   /   \  7     2 / \   / \9   6 3   1

即将一颗二叉树进行左右翻转

思路：递归的将左子树和右子树进行对调

/** * 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)        {reverseTree(root);}        return root;    }    public void reverseTree(TreeNode root)    {        TreeNode temp = null;        temp = root.left;        root.left = root.right;        root.right = temp;        if(root.left!=null){        reverseTree(root.left);}        if(root.right!=null){        reverseTree(root.right);}    }}