不难看出这题用一维前缀和求k倍数的个数
可能会爆int
#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>
using namespace std;
typedef long long LL;
const int N = 1e5 + 10;
LL s[N],a[N];
int n,k;
int cnt[N];

int main(){
    scanf("%d%d",&n,&k);
    for(int i = 1;i <= n;++i){
        scanf("%lld",&a[i]);
        s[i] = s[i - 1] + a[i];
    }
    cnt[0] = 1;
    LL res = 0;
    for(int i = 1;i <= n;++i){
        res += cnt[s[i] % k];
        cnt[s[i] % k]++;
    }
    printf("%lld\n",res);
    return 0;
}