[leetcode.com]算法题目 - 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.

 1 /**
 2  * Definition for binary tree
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 8  * };
 9  */
10 class Solution {
11 public:
12     bool isSameTree(TreeNode *p, TreeNode *q) {
13         // Start typing your C/C++ solution below
14         // DO NOT write int main() function
15         if (NULL==p && NULL==q) return true;
16         
17         if (NULL!=p && NULL==q) return false;
18         
19         if (NULL !=q && NULL==p) return false;
20         
21         if (p->val == q-> val)
22             return (isSameTree(p->left,q->left) && isSameTree(p->right,q->right));
23         else
24             return false;
25     }
26 };
题目答案

思路:采用递归的方法,先判断(1)p和q都为NULL,则返回true;(2)p和q一个是NULL,一个不是NULL,则返回false;(3)如果(1)和(2)都不是,则证明两个tree都不是NULL,判断p->value是否等于q->value,若不等于,则返回false;若等于,则返回(他们的左子树相等 and 他们的右子树相等)。

posted on 2013-09-09 22:23  Horstxu  阅读(194)  评论(0编辑  收藏  举报

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