Submission #5189

# Submission time Handle Problem Language Result Execution time Memory
5189 2014-02-14T00:26:34 Z cki86201 초록색 삼각형 (YDX13_green) C++
1 / 1
1208 ms 1356 KB
#include<stdio.h>
#include<algorithm>
#include<math.h>

typedef long long ll;

const double PI = 3.14159265358979;

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;
	if(n == 3){
		ll tmp = (ll)(x[2]-x[1])*(y[3]-y[1]) - (ll)(x[3]-x[1])*(y[2]-y[1]);
		printf("%.12f\n",tmp>0?tmp/2.0:-tmp/2.0);
		return 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[ord[j]] - an[ord[j-1]] + 2*PI, 2*PI);
			while(na < PI){
				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]/n/(n-1)/(n-2)) * (x[nj] - x[i]) - ((double)now[0]/n/(n-1)/(n-2)) * (y[nj] - y[i]);
		}
	}
	printf("%.12f",ans);
	return 0;
}
# Verdict Execution time Memory Grader output
1 Correct 0 ms 1356 KB Output is correct
2 Correct 0 ms 1356 KB Output is correct
3 Correct 0 ms 1356 KB Output is correct
4 Correct 0 ms 1356 KB Output is correct
5 Correct 0 ms 1356 KB Output is correct
6 Correct 0 ms 1356 KB Output is correct
7 Correct 0 ms 1356 KB Output is correct
8 Correct 0 ms 1356 KB Output is correct
9 Correct 0 ms 1356 KB Output is correct
10 Correct 0 ms 1356 KB Output is correct
11 Correct 220 ms 1356 KB Output is correct
12 Correct 420 ms 1356 KB Output is correct
13 Correct 260 ms 1356 KB Output is correct
14 Correct 1076 ms 1356 KB Output is correct
15 Correct 108 ms 1356 KB Output is correct
16 Correct 1048 ms 1356 KB Output is correct
17 Correct 64 ms 1356 KB Output is correct
18 Correct 168 ms 1356 KB Output is correct
19 Correct 276 ms 1356 KB Output is correct
20 Correct 0 ms 1356 KB Output is correct
21 Correct 1192 ms 1356 KB Output is correct
22 Correct 1192 ms 1356 KB Output is correct
23 Correct 1192 ms 1356 KB Output is correct
24 Correct 1196 ms 1356 KB Output is correct
25 Correct 1196 ms 1356 KB Output is correct
26 Correct 1196 ms 1356 KB Output is correct
27 Correct 1208 ms 1356 KB Output is correct
28 Correct 1200 ms 1356 KB Output is correct
29 Correct 1196 ms 1356 KB Output is correct
30 Correct 1196 ms 1356 KB Output is correct
31 Correct 0 ms 1356 KB Output is correct