Subarray Divisibility.cpp

#include<bits/stdc++.h>
using namespace std;
#define INF 2147483647
#define INFL 9223372036854775807
#define pii pair<int,int>
#define F first
#define S second
#define mp make_pair
#define pb push_back
#define ll long long
#define ull unsigned long long
#define M 1000000007
#define FASTIO ios_base::sync_with_stdio(false);cin.tie(NULL); cout.tie(NULL);
#define take(x) scanf("%d",&x)
#define DE(x) printf("\ndebug %d\n",x);
#define vout(x) for(int i=0;i<x.size();i++) printf("%d ",x[i]);
#define pie acos(-1)
#define MOD 998244353

ll nC2(ll n){
    return n*(n-1)/2;
}

int main(){
    int n;
    take(n);
    ll ara[n+1];
    ara[0] = 0;
    for(int i=1;i<=n;i++){
        cin>>ara[i];
        ara[i]+=ara[i-1];
        ara[i]%=n;
        ara[i] = (ara[i]+n)%n;
    }
    sort(ara,ara+n+1);
    ll res = 0;
    int lastPos = 0;
    for(int i=1;i<=n;i++){
        if( ara[i]!=ara[i-1] ){
            res+=nC2(i-lastPos);
            lastPos = i;
        }
    }
    res+=nC2(n+1-lastPos);
    cout<<res;

}