LeetCode-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.

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比较两棵树是否相同。

/** * 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) {        bool flag;        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 false;        else {            flag = isSameTree( p->left, q->left );             if( !flag ) return false;            flag = isSameTree( p->right, q->right );        }        return flag;    }};