100. Same Tree
problem description
Given two binary trees, write a function to check if they are the same or not.
Two binary trees are considered the same if they are structurally identical and the nodes have the same value.
Example 1:
Input: 1 1
/ \ / \
2 3 2 3
[1,2,3], [1,2,3]
Output: true
Example 2:
Input: 1 1
/ \
2 2
[1,2], [1,null,2]
Output: false
Example 3:
Input: 1 1
/ \ / \
2 1 1 2
[1,2,1], [1,1,2]
Output: false
algorithm thought
树问题,递归解决,首先判断当前节点问题,然后对左右子树分别进行同样的计算。
code
/**
* 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;
if(p&&q&&(p->val==q->val)){
return isSameTree(p->left,q->left)&&isSameTree(p->right,q->right);
}
return false;
}
};
algorithm analysis
相当于对树进行了一次遍历,时间复杂度O(n)
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