[LeetCode100]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.

判断两个二叉树是否相同，如果相同则必须结构相同并且每个节点的值相等

代码：

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