LeetCode #100. Same Tree

题目：https://leetcode.com/problems/same-tree/
分析：注意判断NULL情况，用递归做
代码：（秒AC有木有！）

/**
 * 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(p->val != q->val)
            return false;
        return isSameTree(p->left, q->left) && isSameTree(p->right, q->right);
    }
};