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struct TreeNode {	int val;	TreeNode *left;	TreeNode *right;	TreeNode(int x) : val(x), left(NULL), right(NULL) {}};class Solution {	//check if it is a balanced tree	//so we check the diff between the max height of each branch	//all compare can be done along the way down to calculate max height public:	int CheckHeight(TreeNode* root, bool& ans)	{		if(!root || !ans)//if is is not a balance tree already, we just return			return 0;		int leftHeight = CheckHeight(root->left, ans);		int rightHeight = CheckHeight(root->right, ans);		if(abs(leftHeight-rightHeight) > 1)			ans = false;		return max(leftHeight, rightHeight)+1;	}    bool isBalanced(TreeNode *root) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        //get the height of each subtree		bool ans = true;		CheckHeight(root, ans);		return ans;    }};

second time

/** * Definition for binary tree * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    int isBalancedUtil(TreeNode* root, bool& isValid)    {        if(root == NULL) return 0;        if(!isValid) return -1;        int leftHeight = isBalancedUtil(root->left, isValid);        int rightHeight = isBalancedUtil(root->right, isValid);        if(abs(leftHeight-rightHeight) > 1) isValid = false;        return max(leftHeight, rightHeight)+1;    }    bool isBalanced(TreeNode *root) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        bool ans = true;        isBalancedUtil(root, ans);        return ans;    }};

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