[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.

[解题思路]

非常常见的递归题，先检查当前节点的左右节点是否相同，然后递归检查左子树和右子树。

/** * Definition for binary tree * 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) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        if (p && q)            if (p->val == q->val)                    return (isSameTree(p->left, q->left) && isSameTree(p->right, q->right));            else                return false;        else if ((p == NULL) && (q == NULL))            return true;        else            return false;    }};

[源代码]