poj1113Wall(凸包）

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顺便整理出来一份自己看着比较顺眼的模板

#include <iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<stdlib.h>
#include<vector>
#include<cmath>
#include<queue>
#include<set>
using namespace std;
#define N 1010
#define LL long long
#define INF 0xfffffff
const double eps = 1e-8;
const double pi = 3.141592653;
const double inf = ~0u>>2;
struct Point
{
    double x,y;
    Point(double x=0,double y=0):x(x),y(y) {} //构造函数 方便代码编写
}p[N],ch[N];
typedef Point pointt;
pointt operator + (Point a,Point b)
{
    return Point(a.x+b.x,a.y+b.y);
}
pointt operator - (Point a,Point b)
{
    return Point(a.x-b.x,a.y-b.y);
}
pointt operator * (Point a,double b)
{
    return Point(a.x*b,a.y*b);
}
pointt operator / (Point a,double b)
{
    return Point(a.x/b,a.y/b);
}
bool operator < (const Point &a,const Point &b)
{
    return a.x<b.x||(a.x==b.x&&a.y<b.y);
}
int dcmp(double x)
{
    if(fabs(x)<eps) return 0;
    else return x<0?-1:1;
}
bool operator == (const Point &a,const Point &b)
{
    return dcmp(a.x-b.x)==0&&dcmp(a.y-b.y)==0;
}
//求点积以及利用点积求长度和夹角的函数
double dot(Point a,Point b)
{
    return a.x*b.x+a.y*b.y;
}
//叉积及叉积求面积
double cross(Point a,Point b)
{
    return a.x*b.y-a.y*b.x;
}
double  dis(Point a)
{
    return sqrt(dot(a,a));
}
double mul(Point p0,Point p1,Point p2)
{
    return cross(p1-p0,p2-p0);
}
bool cmp(Point a,Point b)
{
    if(dcmp(mul(p[1],a,b))==0)
        return dis(a-p[1])<dis(b-p[1]);
    else
        return dcmp(mul(p[1],a,b))>0;
}
int Graham(int n)
{
    int i,k = 1,top = 1;
    Point tmp;
    if(n<=3)
    {
        for(i = 1; i <= 3 ; i++)
            ch[i] = p[i];
        return n+1;
    }
    for(i = 1 ; i <= n; i++)
    {
        if(p[i].y<p[k].y||(p[i].y==p[k].y&&p[i].x<p[k].x))
            k = i;
    }
    if(k!=1)
    {
        tmp = p[1];  p[1] = p[k];  p[k] = tmp;
    }
    sort(p+2,p+n+1,cmp);
    ch[top++] = p[1];
    ch[top++] = p[2];
    ch[top++] = p[3];
    for(i = 4; i <= n ;)
    {
        if(top<3||mul(ch[top-2],ch[top-1],p[i])>0)
        {
            ch[top++] = p[i++];
        }
        else  top--;
    }
    return top;
}
int main()
{
    int i,n,r;
    while(scanf("%d%d",&n,&r)!=EOF)
    {
        for(i = 1 ; i <= n ; i++)
        {
            scanf("%lf%lf",&p[i].x,&p[i].y);
        }
        int top = Graham(n);
        ch[top] = p[1];
        double ma;
        ma = 2*pi*r;
        for(i = 1 ; i < top ; i++)
        {
            ma += dis(ch[i]-ch[i+1]);
        }
        printf("%.0f
",ma);
    }
    return 0;
}