Submission #3053331

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Source Code Expand

#include<bits/stdc++.h>
using namespace std;
const int N=4e4+7,mod=1e9+7,inv2=5e8+4;
int n,ans,a[N*50],b[N*50],fac[N],inv[N],f[4007][4007];
int C(int a,int b){return 1ll*fac[a]*inv[b]%mod*inv[a-b]%mod;}
int main()
{
	fac[0]=1;
	for(int i=1;i<=4e4;i++)fac[i]=1ll*fac[i-1]*i%mod;
	inv[0]=inv[1]=1;
	for(int i=2;i<=4e4;i++)inv[i]=1ll*inv[mod%i]*(mod-mod/i)%mod;
	for(int i=2;i<=4e4;i++)inv[i]=1ll*inv[i]*inv[i-1]%mod;
	scanf("%d",&n);
	for(int i=1;i<=n;i++)scanf("%d%d",&a[i],&b[i]),f[2001-a[i]][2001-b[i]]++;
	for(int i=1;i<=4001;i++)
	for(int j=1;j<=4001;j++)
	{
		f[i][j]=(f[i][j]+f[i-1][j])%mod;
		f[i][j]=(f[i][j]+f[i][j-1])%mod;
	}
	for(int i=1;i<=n;i++)ans=(ans+f[2001+a[i]][2001+b[i]])%mod;
	for(int i=1;i<=n;i++)ans=(ans-C(a[i]+a[i]+b[i]+b[i],a[i]+a[i])+mod)%mod;
	ans=1ll*ans*inv2%mod;
	printf("%d",ans);
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:13:16: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
                ^
./Main.cpp:14:74: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  for(int i=1;i<=n;i++)scanf("%d%d",&a[i],&b[i]),f[2001-a[i]][2001-b[i]]++;
                                                                          ^

Judge Result