Submission #5189

#	TimeUTC-0	Username	Problem	Language	Result	Execution time	Memory
5189	2014-02-14 00:26:34	cki86201	초록색 삼각형 (YDX13_green)	C++98	1 / 1	1208 ms	1356 KiB

C

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#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);
 
 
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