답안 #5175

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
5175	2014-02-13T22:45:42 Z	cki86201	초록색 삼각형 (YDX13_green)	C++	0 / 1	864 ms	1352 KB

C

#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);
		int t = (ord[1] == i)?2:1;
		ll now[2] = {0,0};
		for(j=1;j<=n;j++){
			int nj = ord[j];
			if(nj == i)continue;
			now[0] -= x[nj] - x[i], now[1] -= y[nj] - y[i];
			while(ord[t] == i || t == j)now[0] += x[ord[t]] - x[i], now[1] += y[ord[t]] - y[i], 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;
}

Subtask #1

0.0 / 1.0

#	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	156 ms	1352 KB	Output is correct
12	Correct	296 ms	1352 KB	Output is correct
13	Correct	184 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	860 ms	1352 KB	Output is correct
22	Correct	856 ms	1352 KB	Output is correct
23	Correct	856 ms	1352 KB	Output is correct
24	Correct	860 ms	1352 KB	Output is correct
25	Correct	864 ms	1352 KB	Output is correct
26	Correct	856 ms	1352 KB	Output is correct
27	Correct	860 ms	1352 KB	Output is correct
28	Correct	860 ms	1352 KB	Output is correct
29	Correct	860 ms	1352 KB	Output is correct
30	Correct	860 ms	1352 KB	Output is correct
31	Incorrect	0 ms	1352 KB	Output isn't correct