100. Same Tree

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.

思路：一直检查到根节点，不一样的就return false。逻辑一定要清楚。

/** * 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) {        return checkChildren(p, q);    }    bool checkChildren(TreeNode *p, TreeNode *q)    {        if ((p == NULL&&q != NULL) || (p != NULL && q == NULL))    {        return false;    }    if (p == NULL && q == NULL)    {        return true;    }    if (p->val != q->val)    {        return false;    }    return checkChildren(p->left, q->left) && checkChildren(p->right, q->right);    }};