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  1. #include<bits/stdc++.h>
  2. #define FOR(i,a,b) for(long long int i=(a);i<=(b);++i)
  3. #define NFOR(i,a,b) for(long long int i=(a);i>=(b);--i)
  4. #define pb push_back
  5. #define ll long long
  6. #define F first
  7. #define PI 3.14159265358979323846264338327
  8. #define S second
  9. #define all(v) v.begin(),v.end()
  10. #define trace(x) cout << '>' << #x << ':' << x << endl;
  11. #define trace2(x,y) cout<< '>' << #x << ':' << x << " | " << #y << ':' << y << endl;
  12. #define fast ios_base::sync_with_stdio(false); cin.tie(NULL)
  13. #define MOD 1000000007
  14. using namespace std;
  15. ll brr[10004];
  16. void solve()
  17. {
  18. 	ll t,n,m,x,y;
  19.     cin>>n>>m;
  20.     ll arr[n+1];
  21.     FOR(i,1,n)
  22.     cin>>arr[i];
  23.  
  24.     FOR(i,1,n)
  25.     {
  26.     	arr[i]%=m;
  27.     	brr[arr[i]]++;
  28.     }
  29.   long long sum=0;
  30.     FOR(i,0,m-1)
  31.     {
  32.     	if(brr[i]<=0)continue;
  33.     	FOR(j,i,m-1)
  34.     	{
  35.     		if(brr[j]<=0)continue;
  36.     		ll v1=(i+j)%m;
  37.     		ll k=(m-v1)%m;
  38.     		if(k>=j){
  39.     		long long ans=0;
  40.     		if(i==j&&i==k)
  41.     		{
  42.     		     if(brr[i]>=2)
  43.     		      ans+=(1LL*brr[i]*(brr[i]-1)*(brr[i]-2))/6;
  44.     		}
  45.     		else if(i==j)
  46.     		{
  47.     			if(brr[i]>=1){
  48.     			ans+=(1LL*(brr[i])*(brr[i]-1))/2;
  49.     			ans*=brr[k];}
  50.     		}
  51.     		else if(i==k)
  52.     		{
  53.     			if(brr[i]>=1){
  54.     			ans+=(1LL*(brr[i])*(brr[i]-1))/2;
  55.     			ans*=brr[j];}
  56.     		}
  57.     		else if(j==k)
  58.     		{
  59.     		          if(brr[j]>=1){
  60.     		          ans+=(1LL*(brr[j])*(brr[j]-1))/2;
  61.     		          ans*=brr[i];}
  62.     		}
  63.     		else
  64.     		ans+=(1LL*brr[i]*brr[j]*brr[k]);
  65.     		ans=max(ans,0LL);
  66.     		sum+=ans;
  67.  
  68.     		}
  69.     	}
  70.     }
  71.     cout<<sum<<endl;
  72.  
  73. }
  74.  
  75. int main()
  76. {
  77.     fast;
  78.  
  79.     solve();
  80. return 0;
  81. }
Runtime error #stdin #stdout 0s 16144KB
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https://ideone.com/N1AJCt
language:
C++14 (gcc 8.3)
created:
6 years ago
visibility:
secret

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