求凸包周长

来源：互联网发布：百度seo排名点击软件编辑：程序博客网时间：2024/04/28 07:01
#include <map>#include <set>#include <vector>#include <math.h>#include <string>#include <stdio.h>#include <stdlib.h>#include <string.h>#include <iostream>#include <algorithm>#include <functional>const double pi = acos(-1.0);using namespace std;const int MAXN=10005;const double eps=1e-2;int dcmp(double x){    if(fabs(x)<eps)return 0;    if(x>0)return 1;    return -1;}                                                   //弄精度struct Point {    double x,y;}p[MAXN];                                           //搞点double dot(Point a,Point b,Point c){    double s1=b.x-a.x;    double t1=b.y-a.y;    double s2=c.x-a.x;    double t2=c.y-a.y;    return s1*s2+t1*t2;}                                                     //点积int n,res[MAXN],top;//全局变量，n是给出点的个数，top是凸包顶点的个数,res[]存排序后凸包上点的下标bool cmp(Point a,Point b){    if(a.y==b.y)return a.x<b.x;    return a.y<b.y;}bool mult(Point sp,Point ep,Point op){    return (sp.x-op.x)*(ep.y-op.y)>=(ep.x-op.x)*(sp.y-op.y);}void Graham(){    int len;    top=1;    sort(p,p+n,cmp);    if(n==0)return;res[0]=0;    if(n==1)return;res[1]=1;    if(n==2)return;res[2]=2;    for(int i=2;i<n;i++){        while(top&&mult(p[i],p[res[top]],p[res[top-1]]))top--;        res[++top]=i;    }    len=top;    res[++top]=n-2;    for(int i=n-3;i>=0;i--){        while(top!=len&&mult(p[i],p[res[top]],p[res[top-1]]))top--;        res[++top]=i;    }}                                                               //求凸包 double dist(Point a,Point b){    return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));}int main(){    int m,t,l;    cin>>t;    while(t--)        {            cin>>m>>l;            n=m;        for(int i=0;i<m;i++)            scanf("%lf%lf",&p[i].x,&p[i].y);        Graham();        double sum=0;        for(int i=0;i<top;i++)            sum+=dist(p[res[i]],p[res[i+1]]);            sum+=2*pi*l;        printf("%.0lf\n",sum);        if(t!=0)printf("\n");}    return 0;}
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