题目：

题解：

class Solution {
public:int height(TreeNode* root) {if (root == NULL) {return 0;}int leftHeight = height(root->left);int rightHeight = height(root->right);if (leftHeight == -1 || rightHeight == -1 || abs(leftHeight - rightHeight) > 1) {return -1;} else {return max(leftHeight, rightHeight) + 1;}}bool isBalanced(TreeNode* root) {return height(root) >= 0;}
};