leetcode 100. Same Tree

题目描述：

Given two binary trees, write a function to check if they are equal or not.

Two binary trees are considered equal if they are structurally identical and the nodes have the same value.

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