题解 | #二叉树的镜像#

先考虑单层 情况 再考虑多层

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) {
        if(pRoot == null){
            return pRoot;
        }
        TreeNode temp = pRoot.left;
        pRoot.left =  pRoot.right;
        pRoot.right =  temp;
        if(pRoot.left != null){
            Mirror(pRoot.left);
        }
        if(pRoot.right != null){
            Mirror(pRoot.right);
        }
        return  pRoot;
        // write code here
    }
}