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.
代码：
/**
* 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) return true;
int l = maxDepth(root -> left);
int r = maxDepth(root -> right);
return abs(l - r) <= 1 && isBalanced(root -> left) && isBalanced(root -> right);
}
int maxDepth(TreeNode* root) {
if(!root) return 0;
int h1 = 1, h2 = 1;
if(root -> left != NULL)
h1 = maxDepth(root -> left) + 1;
if(root -> right != NULL)
h2 = maxDepth(root -> right) + 1;
return max(h1, h2);
}
};
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