101 Symmetric Tree 判断一颗二叉树是否是镜像二叉树

给定一个二叉树,检查它是否是它自己的镜像(即,围绕它的中心对称)。
例如,这个二叉树 [1,2,2,3,4,4,3] 是对称的。
    1
   / \
  2   2
 / \ / \
3  4 4  3
但是下面这个 [1,2,2,null,3,null,3] 则不是:
    1
   / \
  2   2
   \   \
   3    3
说明:
如果你可以递归地和迭代地解决它就奖励你点数。
详见:https://leetcode.com/problems/symmetric-tree/description/

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    bool isSymmetric(TreeNode* root) {
        if(!root)
        {
            return true;
        }
        return helper(root->left,root->right);
    }
    bool helper(TreeNode* left,TreeNode* right)
    {
        if(!left&&!right)
        {
            return true;
        }
        else if(!left||!right)
        {
            return false;
        }
        else if(left->val!=right->val)
        {
            return false;
        }
        else
        {
            return helper(left->left,right->right)&&helper(left->right,right->left);
        }
    }
};

原文地址:https://www.cnblogs.com/xidian2014/p/8718031.html

时间: 2024-10-10 04:39:40

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