110. Balanced Binary Tree

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110. Balanced Binary Tree

Description

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

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

Hints/Notes

Solution

Language: C++

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/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left),
 * right(right) {}
 * };
 */
class Solution {
public:
    bool balanced = true;

    bool isBalanced(TreeNode* root) {
        traverse(root);
        return balanced;
    }

    int traverse(TreeNode* root) {
        if (!root || !balanced) {
            return 0;
        }

        int left = traverse(root->left);
        int right = traverse(root->right);

        if (abs(left - right) > 1) {
            balanced = false;
            return 0;
        }

        return max(left, right) + 1;
    }
};