Submission #66576679

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Source Code Expand

#include<bits/stdc++.h>
using namespace std;
#define endl '\n'
#define int long long
const int N=3e5+10;
int dx[]={0,1,0,-1},dy[]={1,0,-1,0};
map<int,int> mp;
int n,m,k;
int a[N],b[N];
void slove(){
    cin>>n>>m;
    for(int i=1;i<n;i++) cin>>a[i];
    if(m%3!=0) cout<<0<<endl;
    else{
        int x=m/3;
        mp[0]++;
        int sum=0;
        for(int i=1;i<n;i++){
            sum+=a[i];
            sum%=m;
            mp[sum]++;
            // cout<<sum<<' ';
        }
        // cout<<endl;
        int ans=0;
        for(int i=0;i<=m/2;i++){
            if(mp[i]!=0&&mp[i+x]!=0&&mp[i+2*x]!=0){
                ans+=mp[i]*mp[i+x]*mp[i+2*x];
                mp[i]=mp[i+x]=mp[i+2*x]=0;
            }
        }
        cout<<ans<<endl;
    }
}
signed main(){
ios::sync_with_stdio(false);
cin.tie(nullptr);
    int T=1;
    // cin>>T;
    while(T--){
        slove();
    }
}

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