翻转二叉树-LeetCode

题目：

链接：https://leetcode-cn.com/problems/invert-binary-tree/

思路：

1. 这题在剑指offer上也有，就是递归，然后交换下左右子树就可以了

代码：

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