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:

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

Example 2:

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

Example 3:

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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;
            
    }
};




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