Balanced Binary Tree（C++平衡二叉樹）

/**
 * 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:
    bool isBalanced(TreeNode* root) {
        bool tag = true;
        height(root,tag);
        return tag;
    }
    
    int height(TreeNode* root,bool &tag) {
	if(root==NULL) return -1;
	int l = height(root->left,tag);
	int r = height(root->right,tag);
	if(abs(l-r)>1) tag=false;
	return max(l,r)+1;
    }
};