[蓝桥杯]优化过程的一道题

#include <iostream>
#include <algorithm>
using namespace std;
typedef long long LL;
const int N = 100010;
int n, k;
LL s[N], cnt[N];
int main()
{
    scanf("%d%d", &n, &k);
    for (int i = 1; i <= n; i ++ )
    {
        scanf("%lld", &s[i]);
        s[i] += s[i - 1];//前缀和
    }
    LL res = 0;
    cnt[0] = 1;
    for (int i = 1; i <= n; i ++ )
    {
        res += cnt[s[i] % k];//使用数组存储余数
        cnt[s[i] % k] ++ ;
    }
    printf("%lld\n", res);
    return 0;
}