# 110.Balanced Binary Tree

## 刷题内容

• https://leetcode.com/problems/balanced-binary-tree/

Given a binary tree, determine if it is height-balanced.

For this problem, a height-balanced binary tree is defined as:

a binary tree in which the depth of the two subtrees of every node never differ by more than 1.

Example 1:

Given the following tree [3,9,20,null,null,15,7]:

3
/ \
9  20
/  \
15   7
Return true.

Example 2:

Given the following tree [1,2,2,3,3,null,null,4,4]:

1
/ \
2   2
/ \
3   3
/ \
4   4
Return false.


˼· **- ʱ�临�Ӷ�: O(n)*- �ռ临�Ӷ�: O(1)***

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/**
* 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 isBalanced(TreeNode* root) {
if(root == nullptr)
return true;
return abs(height(root ->left) - height(root ->right)) <= 1 && isBalanced(root ->left) && isBalanced(root ->right);
}
int height(TreeNode* root){
if(root == nullptr)
return 0;
return max(height(root ->left),height(root ->right)) + 1;
}
};


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