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 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.

解法：原理如DFS，先判断左节点，然后判断右节点

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

//其他写法一
class Solution {
public:
    bool isSameTreeUtil(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 isSameTreeUtil(p->left, q->left) && isSameTreeUtil(p->right, q->right);
        }
        else return false;
    }
    bool isSameTree(TreeNode *p, TreeNode *q) {
        return isSameTreeUtil(p, q);
    }
};

//其他写法二
class Solution {
public:
    bool isSameTree(TreeNode *p, TreeNode *q) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        if (p == NULL || q == NULL) {
            return p == NULL && q == NULL;
        }
        return 
            p->val == q->val && 
            isSameTree(p->left, q->left) && isSameTree(p->right, q->right);
    }
};

leetcode_100_Same Tree

标签：leetcode   c++   tree   dfs   

原文地址：http://blog.csdn.net/keyyuanxin/article/details/43851603