[leetcode][tree] Same Tree

题目：

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(NULL == p && NULL == q) return true;        if(NULL == p || NULL == q || p->val != q->val) return false;        return isSameTree(p->left, q->left) && isSameTree(p->right, q->right);    }};