Pagini recente » Cod sursa (job #1281715) | Cod sursa (job #1999862) | Cod sursa (job #2369263) | Cod sursa (job #1057554) | Cod sursa (job #1922531)
#include <fstream>
#include <algorithm>
#include <iomanip>
using namespace std;
ifstream f("infasuratoare.in");
ofstream g("infasuratoare.out");
struct el{double x; double y;};
el a[120001],aa,st[120001];
int n,i,poz;
struct mm{double x; double y;};
double xx,yy,minix,miniy;
double calc(int n)
{
return (a[n].y-a[n].x)/(a[1].y-a[1].x);
}
double cal(el aa, el b, el c)
{
return (b.x-aa.x)*(c.y-aa.y)-(b.y-aa.y)*(c.x-aa.x);
}
int cmp(el aa, el bb)
{
double ads=cal(a[1],aa,bb);
return ads< 0;
}
int main()
{
f>>n;
f>>minix>>miniy;
a[1].x=minix;
a[1].y=miniy;
for(i=2;i<=n;i++)
{
f>>xx>>yy;
a[i].x=xx;
a[i].y=yy;
if(a[i].x<minix)
{
minix=a[i].x;
miniy=a[i].y;
poz=i;
}
else
if(a[i].x==minix and a[i].y<miniy)
{
miniy=a[i].y;
poz=i;
}
}
aa=a[poz];
a[poz]=a[1];
a[1]=aa;
sort(a+2,a+n+1,cmp);
st[1].x=a[1].x;
st[1].y=a[1].y;
st[2].x=a[2].x;
st[2].y=a[2].y;
int s=2;
for(i=3;i<=n;i++)
{
while(s>=2 and cal(st[s],st[s-1],a[i])<0)
s--;
s++;
st[s].x=a[i].x;
st[s].y=a[i].y;
}
g<<s<<'\n';
for(i=s;i>=1;i--)
g<<fixed<<setprecision(9)<<st[i].x<<" "<<st[i].y<<'\n';
return 0;
}