BalancedTree.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:
    pair<bool, int> isBalfast(TreeNode* root){
        if(root==NULL){
             pair<bool, int> p;
             p = make_pair(true, 0);
             return p;
        }
        pair<bool, int> left = isBalfast(root->left);
        pair<bool, int> right = isBalfast(root->right);
        bool diff = abs(left.second - right.second)<=1;
        pair<bool, int> ans;
        ans.second = max(left.second, right.second)+1;
        if(left.first && right.first && diff) ans.first = true;
        else ans.first = false;

        return ans;
    }
    bool isBalanced(TreeNode* root) {
        return isBalfast(root).first;
    }
};