ZOJ1453

求一个凸包= =...直接上模板

#include<bits/stdc++.h>
using namespace std;
int n;
void Gao()
{
    vector<VEC> a,b;
    for (int i=0;i<n;i++)
    {
        VEC tem;
        cin>>tem.x>>tem.y;
        a.push_back(tem);
    }
    b=convex_hull(a);
    double ans=0.0;
    for (int i=0;i<b.size();i++)
    {
        int j=i+1;
        if (j==b.size())
            j=0;
        VEC tem=b[i]-b[j];
        double xx=tem.x,yy=tem.y;
        ans+=sqrt(xx*xx+yy*yy);
    }
    printf("%.2lf\n",ans);
}
int main()
{
    //freopen("a.in","r",stdin);
    while (cin>>n &&n)
        Gao();
    return 0;
}