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https://github.com/Kiritow/OJ-Problems-Source.git
synced 2024-03-22 13:11:29 +08:00
47 lines
1.2 KiB
C++
47 lines
1.2 KiB
C++
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#include<cmath>
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#include<cstdio>
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#include<iostream>
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#include<algorithm>
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#define eps 1e-8
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#define pi acos(-1.0)
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using namespace std;
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const int N=1000;
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struct Point{double x, y;}p[N];
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double ans[2*N];
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long long C(int a,int b){
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long long ans=1;
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for(int i=0;i<b;i++) ans*=(a-i);
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for(int i=2;i<=b;i++) ans/=i;
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return ans;
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}
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int main(){
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int t,n;
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scanf("%d",&t);
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while(t--){
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scanf("%d",&n);
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for(int i=0;i<n;i++)
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scanf("%lf%lf",&p[i].x,&p[i].y);
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long long res=0;
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for(int i=0;i<n;i++){
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for(int j=0;j<n;j++){
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if(j==i) continue;
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double tmp=atan2(p[j].y-p[i].y,p[j].x-p[i].x);
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if(tmp<=-eps) tmp+=2*pi;
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j<i?ans[j]=tmp:ans[j-1]=tmp;
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}
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sort(ans,ans+n-1);
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int k=1;
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long long re2=0;
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for(int j=0;j<n-1;j++)
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ans[j+n-1]=ans[j]+2*pi;
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for(int j=0;j<n-1;j++){
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while(fabs(ans[k]-ans[j])-pi<0) k++;
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if(k-j-1>=2) re2+=C(k-j-1,2);
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}
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res+=C(n-1,3)-re2;
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}
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printf("%I64d\n",C(n,4)-res);
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}
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return 0;
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}
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