110. 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) {}
 * };
 */
class Solution {
public:
int height(TreeNode* root)
    {
        if (!root) return 0;
        return 1 + max(height(root->left), height(root->right));
    }
    bool isBalanced(TreeNode* root) {
        if (!root) return true;
        int balance = height(root->left) - height(root->right);
        if (balance > 1 || balance < -1) return false;
        if (!isBalanced(root->left) || !isBalanced(root->right)) return false;
        return true;
    }
};