题解 | #牛群的轴对称结构#

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 root TreeNode类 
     * @return bool布尔型
     */
    public boolean isSymmetric (TreeNode root) {
        return dfs(root.left,root.right);
        // write code here
    }
    public boolean dfs(TreeNode left,TreeNode right){
        if(left==null&&right==null){
            return true;
        }
        if(left==null||right==null||left.val!=right.val){
            return false;
        }
        if(!dfs(left.left,right.right)||!dfs(left.right,right.left)){
            return false;
        }
        return true;
    }
}

java代码