tubao pku1113

#include<stdio.h>
#include<math.h>
#include<string.h>
#include<algorithm>
using namespace std;
#define N 1001
const double pi=acos(-1.0);
struct point 
{
    int x,y;
}node[N];
int s[N];
int top;
int cmp(point a,point b)
{
    if(a.y==b.y)
        return a.x<b.x;
    return a.y<b.y;
}
double chaji(point p0,point p1,point p2)
{
    return ((p1.x-p0.x)*(p2.y-p0.y)-(p1.y-p0.y)*(p2.x-p0.x));
}
double dis(point a,point b)
{
    return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
}
void tubao(int n)
{
    int i,temp;
    sort(node,node+n,cmp);
    top=-1;
    s[++top]=0;
    s[++top]=1;
    for(i=2;i<n;i++)
    {
        while(top>=1&&chaji(node[s[top-1]],node[i],node[s[top]])>=0 )
            top--;
        s[++top]=i;
    }
    temp=top;
    s[++top]=n-2;
    for(i=n-3;i>=0;i--)
    {
        while(top>=temp+1&&chaji(node[s[top-1]],node[i],node[s[top]])>=0)
            top--;
        s[++top]=i;
    }
}
int main()
{
    int i,n,l;
    double ans;
    while(scanf("%d%d",&n,&l)!=EOF)
    {
        for(i=0;i<n;i++)
            scanf("%d%d",&node[i].x,&node[i].y);
        tubao(n);
        ans=0;
        for(i=0;i<top;i++)
            ans+=dis(node[s[i]],node[s[i+1]]);
        ans+=2*pi*l;
        printf("%.0lf",ans);
    }
    return 0;
}

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