2517. Maximum Tastiness of Candy Basket

You are given an array of positive integers price where price[i] denotes the price of the ith candy and a positive integer k.

The store sells baskets of k distinct candies. The tastiness of a candy basket is the smallest absolute difference of the prices of any two candies in the basket.

Return the maximum tastiness of a candy basket.

class Solution {
    bool helper(vector<int>& A, int k, long long m) {
        int res = 1, last = A[0];
        for(int i = 1; i < A.size() and res < k; i++) {
            if(last + m <= A[i]) {
                last = A[i];
                res += 1;
            }
        }
        return res >= k;
    }
public:
    int maximumTastiness(vector<int>& A, int k) {
        sort(begin(A), end(A));
        long long l = 0, r = 1e9 + 1, res = 0;
        while(l <= r) {
            long long m = l + (r - l) / 2;
            bool pass = helper(A,k,m);
            if(pass) {
                res = max(res,m);
                l = m + 1;
            } else r = m - 1;
        }
        return res;
    }
};