LeetCode/110.cpp at master · nitin-maharana/LeetCode · GitHub

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/*
 * Written by Nitin Kumar Maharana
 * nitin.maharana@gmail.com
 */

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */

class Solution {
    bool flag;
public:

    int isBalancedUtil(TreeNode *root)
    {
        if(!flag)
            return 0;

        if(!root)
            return 0;

        int l = isBalancedUtil(root->left);

        if(!flag)
            return 0;

        int r = isBalancedUtil(root->right);

        if(!flag)
            return 0;

        if(abs(l-r) > 1)
        {
            flag = false;
            return 0;
        }

        return ((l < r) ? (r+1) : (l+1));
    }

    bool isBalanced(TreeNode* root) {
        flag = true;
        isBalancedUtil(root);
        return flag;
    }
};

//One more solution without global variable.
class Solution {
    int isBalancedUtil(TreeNode* root)
    {
        if(root == nullptr)
            return 0;

        int l, r;

        l = isBalancedUtil(root->left);

        if(l == -1)
            return -1;

        r = isBalancedUtil(root->right);

        if(r == -1)
            return -1;

        if(abs(l - r) > 1)
            return -1;

        return max(l, r) + 1;
    }
public:
    bool isBalanced(TreeNode* root) {
        return (isBalancedUtil(root) != -1);
    }
};