110-balanced-binary-tree.cpp

class Solution {
public:
    struct BalanceHeight {
        bool balanced;
        int height;
    };
    
    BalanceHeight checkBalance(TreeNode* root) {
        if (root == nullptr) {
            return {true, -1};
        }
        
        BalanceHeight left = checkBalance(root->left);
        if (!left.balanced) {return {false, 0}; }
        
        BalanceHeight right = checkBalance(root->right);
        if (!right.balanced) {return {false, 0}; }
        
        bool balanced = abs(left.height - right.height) <= 1;
        int height = std::max(left.height, right.height) + 1;
        return {balanced, height};
    }
    
    bool isBalanced(TreeNode* root) {
        return checkBalance(root).balanced;
    }
};