Balanced Binary Tree.cpp

/**
 * 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) {}
 * };
 */

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