leetcode_100_Same Tree (C++)(easy)
2016-04-19 11:01
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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:判断两个二叉树是不是相等 首先要结构相等 此外对应节点值相等 采用递归的方法 首先鉴定两棵树的root是否相等 再判断其左右子树的结构相等与否。本题难点在于边界条件的测试。两棵树其中有一树为空另一个树不空时的测试,以及两棵树都不空,但值不相等的情况下进行测试。
/**
* 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) {
if(p == NULL && q == NULL)
return true;
while(p != NULL && q != NULL)
{
if (p -> val == q -> val )
{
return(isSameTree(p -> left , q -> left) && isSameTree(p -> right , q -> right));
}
else
return false;
}
if((p == NULL && q != NULL)^(p != NULL && q == NULL) == 1)/*异或为1表示一棵树空另一棵不空的情况*/
return false;
}
};
Two binary trees are considered equal if they are structurally identical and the nodes have the same value.
思路:判断两个二叉树是不是相等 首先要结构相等 此外对应节点值相等 采用递归的方法 首先鉴定两棵树的root是否相等 再判断其左右子树的结构相等与否。本题难点在于边界条件的测试。两棵树其中有一树为空另一个树不空时的测试,以及两棵树都不空,但值不相等的情况下进行测试。
/**
* 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) {
if(p == NULL && q == NULL)
return true;
while(p != NULL && q != NULL)
{
if (p -> val == q -> val )
{
return(isSameTree(p -> left , q -> left) && isSameTree(p -> right , q -> right));
}
else
return false;
}
if((p == NULL && q != NULL)^(p != NULL && q == NULL) == 1)/*异或为1表示一棵树空另一棵不空的情况*/
return false;
}
};
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