👨‍🏫 题目地址

😋 AC code

/**
 * 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)
	{
        if(root == null)
            return root;
		TreeNode t = root.left;
		root.left = root.right;
		root.right = t;
		if (root.left != null)
			invertTree(root.left);
		if (root.right != null)
			invertTree(root.right);
		return root;
	}
}