这次写的凸包用的是Graham scan算法
就数据结构上只是简单地运用了一个栈
#include<stdio.h>
#include<cmath>
#include<algorithm>
//#define LOCAL
using namespace std;
const int max1=1000;
typedef struct point
{
int x;
int y;
}point;
int cp(point a,point b,point c)
{
c.x-=a.x;
c.y-=a.y;
b.x-=a.x;
b.y-=a.y;
return (b.x*c.y-b.y*c.x)>0;
}
int cmp(point a,point b)
{
if(a.y!=b.y) return a.y<b.y;
else return a.x<b.x;
}
double len(point a,point b)
{
return sqrt((a.x-b.x)*(a.x-b.x)*1.0+(a.y-b.y)*(a.y-b.y)*1.0);
}
int main()
{
#ifdef LOCAL
freopen("data.in","r",stdin);
#endif // LOCAL
int t;
point a1[max1+5],a2[max1+5];
int N,L;
int top,mtop,i;
double ans;
scanf("%d",&t);
while(t--)
{
ans=0;
scanf("%d%d",&N,&L);
for(i=0;i<N;i++) scanf("%d%d",&a1[i].x,&a1[i].y);
sort(a1,a1+N,cmp);
a2[0]=a1[0];
for(i=1,top=0;i<N;i++)//寻找最低点到最高点的右凸包
{
while(top!=0&&!cp(a2[top-1],a2[top],a1[i]))//在这里如果两条向量在同一条直线上的话(即CP==0)，就将a2【top】弹出
//换成距离更远的点
top--;
a2[++top]=a1[i];
}
a2[++top]=a1[N-1];
mtop=top;
//for(i=0;i<top;i++) printf("%d %d\n",a2[i].x,a2[i].y);
for(i=N-2;i>=0;i--)//寻找最低点到最高点的左凸包
{
while(top!=mtop&&!cp(a2[top-1],a2[top],a1[i]))
top--;
a2[++top]=a1[i];
}
for(i=0;i<top;i++)
{
ans+=len(a2[i],a2[(i+1)%top]);
}
ans+=2*L*3.14159;
printf("%.0lf\n",ans);//四舍五入就行
if(t!=0) printf("\n");
}
return 0;
}