#include<stdio.h>
#include<algorithm>
#include<math.h>
typedef long long ll;
const double PI = 3.141592653589793238;
int x[2020], y[2020], ord[2020];
double an[2020];
int n;
bool comp(const int &a,const int &b){return an[a] < an[b];}
int main()
{
scanf("%d",&n);
int i, j;
for(i=1;i<=n;i++)scanf("%d%d",x+i,y+i);
if(n<=2)return printf("0")&0;
for(i=1;i<=n;i++)ord[i] = i;
double ans = 0;
for(i=1;i<=n;i++){
for(j=1;j<=n;j++)an[j] = atan2(y[j] - y[i], x[j] - x[i]);
std::sort(ord+1,ord+1+n,comp);
ll now[2] = {0,0};
int t = 1;
double na = 0;
for(j=1;j<=n;j++){
int nj = ord[j];
if(j>1)na -= fmod(an[nj] - an[ord[j-1]] + 2*PI, 2*PI);
while(na < PI+1e-10){
now[0] += x[ord[t]] - x[i];
now[1] += y[ord[t]] - y[i];
na += fmod(an[ord[t%n+1]] - an[ord[t]] + 2*PI, 2*PI);
t = t%n + 1;
}
now[0] -= x[nj] - x[i], now[1] -= y[nj] - y[i];
ans += (double)now[1] * (x[nj] - x[i]) - (double)now[0] * (y[nj] - y[i]);
}
}
printf("%.12f",ans/n/(n-1)/(n-2));
return 0;
}
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Correct |
0 ms |
1352 KB |
Output is correct |
| 2 |
Correct |
0 ms |
1352 KB |
Output is correct |
| 3 |
Correct |
0 ms |
1352 KB |
Output is correct |
| 4 |
Correct |
0 ms |
1352 KB |
Output is correct |
| 5 |
Correct |
0 ms |
1352 KB |
Output is correct |
| 6 |
Correct |
0 ms |
1352 KB |
Output is correct |
| 7 |
Correct |
0 ms |
1352 KB |
Output is correct |
| 8 |
Correct |
0 ms |
1352 KB |
Output is correct |
| 9 |
Correct |
0 ms |
1352 KB |
Output is correct |
| 10 |
Correct |
0 ms |
1352 KB |
Output is correct |
| 11 |
Correct |
184 ms |
1352 KB |
Output is correct |
| 12 |
Correct |
348 ms |
1352 KB |
Output is correct |
| 13 |
Correct |
224 ms |
1352 KB |
Output is correct |
| 14 |
Correct |
904 ms |
1352 KB |
Output is correct |
| 15 |
Correct |
88 ms |
1352 KB |
Output is correct |
| 16 |
Correct |
876 ms |
1352 KB |
Output is correct |
| 17 |
Correct |
52 ms |
1352 KB |
Output is correct |
| 18 |
Correct |
140 ms |
1352 KB |
Output is correct |
| 19 |
Correct |
228 ms |
1352 KB |
Output is correct |
| 20 |
Correct |
0 ms |
1352 KB |
Output is correct |
| 21 |
Correct |
1000 ms |
1352 KB |
Output is correct |
| 22 |
Correct |
996 ms |
1352 KB |
Output is correct |
| 23 |
Correct |
1004 ms |
1352 KB |
Output is correct |
| 24 |
Correct |
996 ms |
1352 KB |
Output is correct |
| 25 |
Correct |
1008 ms |
1352 KB |
Output is correct |
| 26 |
Correct |
1004 ms |
1352 KB |
Output is correct |
| 27 |
Correct |
1004 ms |
1352 KB |
Output is correct |
| 28 |
Correct |
1000 ms |
1352 KB |
Output is correct |
| 29 |
Correct |
1000 ms |
1352 KB |
Output is correct |
| 30 |
Correct |
992 ms |
1352 KB |
Output is correct |
| 31 |
Incorrect |
0 ms |
1352 KB |
Output isn't correct |
