# Balanced Binary Tree Problem

## Description

LeetCode Problem 110.

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 left and right subtrees of every node differ in height by no more than 1.

Example 1:

``````1
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Input: root = [3,9,20,null,null,15,7]
Output: true
``````

Example 2:

``````1
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Input: root = [1,2,2,3,3,null,null,4,4]
Output: false
``````

Example 3:

``````1
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Input: root = []
Output: true
``````

Constraints:

• The number of nodes in the tree is in the range [0, 5000].
• -10^4 <= Node.val <= 10^4

## Sample C++ Code

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class Solution {
public:
bool is_balanced;

int bfs(TreeNode* node, int h) {
if (node == NULL)
return h-1;
int left_h = bfs(node->left, h+1);
int right_h = bfs(node->right, h+1);
if (abs(left_h-right_h) > 1)
is_balanced = false;
return max(left_h, right_h);
}

bool isBalanced(TreeNode* root) {
is_balanced = true;
bfs(root, 1);
return is_balanced;

}
};
``````