LeetCode226、翻转二叉树

题目描述：
https://leetcode-cn.com/problems/invert-binary-tree/

解法 :

/**
 * 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 {
    
    
    public TreeNode invertTree(TreeNode root) {
    
    
        //从递归的思维去考虑的话，我们只需要分别反转左右子树即可
        if(root==null) return null;
        //交换其左右结点的值
        TreeNode temp = root.right;
        root.right = root.left;
        root.left = temp;
        //我们不需要用到其返回值，只关注其函数的定义——反转左子树和右子树
        invertTree(root.left);
        invertTree(root.right);
        return root;  

    }
}