HACKERRANK consecutive-subsequences Solution

| August 30, 2016

The correct, optimal and working solution for programming question consecutive-subsequences on hackerrank

/*
 *  Author: Arpit Bhayani
 *  http://arpitbhayani.me
 */
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <climits>
#include <deque>
#include <iostream>
#include <list>
#include <limits>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <vector>

#define ll long long

#define MIN(a, b) a < b ? a : b
#define MAX(a, b) a > b ? a : b

using namespace std;

int readline(char *str) {
    int i = 0;
    char ch;
    while((ch = getchar()) != '\n') {
        str[i++] = ch;
    }
    str[i] = '\0';
    return i;
}

int main(int argc, char *argv[]) {
    int t;
    scanf("%d", &t);

    while(t--) {
        int n, k;
        scanf("%d%d", &n, &k);
        ll int * counts = (ll int *) calloc(100, sizeof(ll int));
        counts[0] = 1;

        ll int sum = 0;
        for(int i = 0 ; i < n ; i++) {
            int x;
            scanf("%d", &x);
            sum += x;
            if(sum >= k) {
                sum %= k;
            }
            counts[sum]++;
        }

        ll int count = 0;
        for(int i = 0 ; i < k; i++) {
            count += ((counts[i] * (counts[i] - 1)) / 2);
        }
        printf("%lld\n", count);

        free(counts);
    }

    return 0;
}