oj.uz

답안 #5164

# 제출 시각 아이디 문제 언어 결과 실행 시간 메모리
5164 2014-02-13T19:53:30 Z cki86201 초록색 삼각형 (YDX13_green) C++
0 / 1
 0 ms 1352 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);
	for(i=1;i<=n;i++)ord[i] = i;
	ll 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 += (x[nj] - x[i]) * now[1] - (y[nj] - y[i]) * now[0];
		}
	}
	printf("%.12f",(double)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 Incorrect 0 ms 1352 KB Output isn't correct
7 Halted 0 ms 0 KB -