Submission #5173

# Submission time Handle Problem Language Result Execution time Memory
5173 2014-02-13T21:32:15 Z cki86201 초록색 삼각형 (YDX13_green) C++
0 / 1
864 ms 1352 KB
#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];}

inline ll ccw(int a,int b,int c)
{
	return (ll)(x[b]-x[a]) * (y[c]-y[a]) - (ll)(x[c]-x[a]) * (y[b]-y[a]);
}

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;
		if(ord[t] == i)t = t%n + 1;
		for(j=1;j<=n;j++){
			int nj = ord[j];
			if(nj == i)continue;
			if(j != t)now[0] -= x[nj] - x[i], now[1] -= y[nj] - y[i];
			else while(ord[t] == i || t == j)t = t%n + 1;
			while(t!=j && ccw(i,ord[j],ord[t]) > 0){
				now[0] += x[ord[t]] - x[i];
				now[1] += y[ord[t]] - y[i];
				t = t%n + 1;
				if(ord[t] == i)t = t%n + 1;
			}
			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;
}
# Verdict Execution time Memory 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 152 ms 1352 KB Output is correct
12 Correct 296 ms 1352 KB Output is correct
13 Correct 188 ms 1352 KB Output is correct
14 Correct 780 ms 1352 KB Output is correct
15 Correct 76 ms 1352 KB Output is correct
16 Correct 752 ms 1352 KB Output is correct
17 Correct 44 ms 1352 KB Output is correct
18 Correct 120 ms 1352 KB Output is correct
19 Correct 196 ms 1352 KB Output is correct
20 Correct 0 ms 1352 KB Output is correct
21 Correct 852 ms 1352 KB Output is correct
22 Correct 864 ms 1352 KB Output is correct
23 Correct 860 ms 1352 KB Output is correct
24 Correct 864 ms 1352 KB Output is correct
25 Correct 864 ms 1352 KB Output is correct
26 Correct 860 ms 1352 KB Output is correct
27 Correct 864 ms 1352 KB Output is correct
28 Correct 860 ms 1352 KB Output is correct
29 Correct 856 ms 1352 KB Output is correct
30 Correct 852 ms 1352 KB Output is correct
31 Incorrect 0 ms 1352 KB Output isn't correct