题目描述
给定一个二叉树，判断它是否是 平衡二叉树

解题思想
使用递归依次计算左子树的高度和右子树的高度

代码

class Solution {
public:
    int height(TreeNode* node) {
        if (node == nullptr) return 0;
        
        int leftT = height(node->left);
        if (leftT == -1) return -1;
        int rightT = height(node->right);
        if (rightT == -1) return -1;
        
        if (abs(leftT - rightT) > 1) 
            return -1;

        else
            return 1 + max(leftT, rightT);
    }


    bool isBalanced(TreeNode* root) {
        return height(root) == -1 ? false : true;
    }
};