JZ18 二叉树的镜像

https://www.nowcoder.com/practice/a9d0ecbacef9410ca97463e4a5c83be7

这题其实挺简单的，就一个普通的交换

import java.util.*;

/*
 * public class TreeNode {
 *   int val = 0;
 *   TreeNode left = null;
 *   TreeNode right = null;
 *   public TreeNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param pRoot TreeNode类 
     * @return TreeNode类
     */
    public TreeNode Mirror (TreeNode pRoot) {
        // write code here
        if (pRoot == null) return null;
        
        TreeNode node = pRoot.right;
        pRoot.right = pRoot.left;
        pRoot.left = node;
        
        Mirror(pRoot.right);
        Mirror(pRoot.left);
        
        return pRoot;
    }
}