LeetCode Symmetric Tree

Description

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).

For example, this binary tree is symmetric:

1
/
2 2
/ \ /
3 4 4 3
But the following is not:
1
/
2 2
\
3 3

The original problem is here.

The original code is here.

My Solution

I solve this problem in C++, as below:

/*
*Symmetric Tree
*Author: shuaijiang
*Email: zhaoshuaijiang8@gmail.com
*/
#include<iostream>
#include<math.h>
#include<stdlib.h>
using namespace std;

/**
 * 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 == NULL)
            return true;
        return isSym(root->left,root->right);
    }
    bool isSym(TreeNode *p, TreeNode *q){
        if(p==NULL && q==NULL)
            return true; 
        if(p==NULL && q!= NULL)
            return false;
        if(p!=NULL && q==NULL)
            return false;
        if(p->val != q->val)
            return false;
        if(isSym(p->left,q->right) && isSym(p->right,q->left)){
            return true;
        }
        return false;
    }
};

Note

This problem is similar to Same Tree. In the process, recursion is needed.