Interview Question 04.04. Check balance
Topic link
Source: LeetCode
Link: https://leetcode-cn.com/problems/check-balance-lcci/
Title description
Implement a function to check whether the binary tree is balanced. In this problem, the definition of a balanced tree is as follows: For any node, the height difference between its two subtrees does not exceed 1.
Example 1:
a given binary tree [3,9,20, null, null, 15,7]
. 3
/
. 9 20 is
/
15. 7
returns true.
Example 2:
given binary tree [1,2,2,3,3, null, null, 4,4 &]
. 1
/
2 2
/
. 3. 3
/
. 4. 4
returns false.
Topic analysis
Top-down recursion
/**
* 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:
int height(TreeNode* root){
if(root==NULL){
return 0;
}else{
return max(height(root->left),height(root->right)) +1;
}
}
bool isBalanced(TreeNode* root) {
if(root==NULL){
return true;
}else{
return abs(height(root->left)-height(root->right))<=1 && isBalanced(root->left) && isBalanced(root->right);
}
}
};