点开有惊喜：https://www.bilibili.com/video/BV1oRd6YXE76/?spm_id_from=333.337.search-card.all.click

题解：

#include<bits/stdc++.h>
using namespace std;
int n,k,m;
const int N=1e5+10;
int a[N],s[N],cnt,l,r,sum;
int main(){
    cin>>n>>k>>m;
    for(int i=1;i<=n;i++){
        cin>>a[i];
        s[i]=s[i-1]+a[i];
    }
    for(int i=k;i<=n;i++){
        l=i-k+1;
        r=i;
        sum=s[r]-s[l-1];
        if(sum%m==0){
            cnt++;
        }
    }
    cout<<cnt;
    return 0;
}