[leetcode](https://oj.leetcode.com/problems/same-tree/) 一道判断两棵树是否相同的题：
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.
直接写递归了，代码行数非常少
~~~
/**
* 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) {
if(p == NULL && q == NULL)return true;
if(p == NULL && q != NULL)return false;
if(p != NULL && q == NULL)return false;
if(p->val == q->val)return isSameTree(p->left, q->left) && isSameTree(p->right, q->right);
else return false;
}
};
~~~
也可以用队列对两棵二叉树层次遍历，在遍历的同时判断节点是否相同。
