poj 1696Space Ant

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学习网站：

http://www.cnblogs.com/Booble/archive/2011/02/28/1967179.html

http://blog.csdn.net/lyy289065406/article/details/6648614

卷包裹算法

#include <cstdio>#include <cstring>using namespace std;struct point{    int x,y;};int dis(point a,point b){    return (a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y);}int det(int x1,int y1,int x2,int y2){    return x1*y2-x2*y1;}int cor(point b,point a,point d,point c){    return  det(b.x-a.x,b.y-a.y,d.x-c.x,d.y-c.y);}int main(){    //freopen("D:\\INPUT.txt","r", stdin);    int cas,n,fi,miny,minx;    cin>>cas;    while(cas--){        int num;        miny=101;        minx=101;        cin>>n;        point p[51];//point* p=new point[n+1];        int line[51];//int* line=new int[n+1];        int fii;        bool vis[51];//bool* vis=new bool[n+1];        memset(vis,0,sizeof(vis));        int i,j,k;        for(i=0;i<n;i++){            cin>>num;            cin>>p[i].x>>p[i].y;            if(p[i].y<miny||(p[i].y==miny&&minx>p[i].x)){                miny=p[i].y;                minx=p[i].x;                fi=i;            }        }        line[1]=fi;        //cout<<"fi: "<<fi<<endl;        vis[fi]=true;        line[0]=1;        while(n!=line[0]){            for(i=0;i<n;i++){                if(!vis[i]){                    fii=i;                    break;                }            }            //cout<<"基准点: "<<i-1<<' '<<fii<<' ';            for(i=0;i<n;i++){                if(i!=fii&&!vis[i]){                    int temp=cor(p[fii],p[fi],p[i],p[fi]);                    if(temp<0||(!temp&&dis(p[fi],p[fii])>dis(p[fi],p[i]))){                        fii=i;                    }                }            }            //cout<<"新基准点: "<<i-1<<' '<<fii<<' ';            line[++line[0]]=fi=fii;            vis[fii]=true;            //cout<<fii+1<<' '<<line[0]<<' '<<line[]<<endl;        }        //cout<<'!'<<vis[8]<<endl;        cout<<line[0];        for(i=1;i<=n;i++){            cout<<' '<<line[i]+1;        }        cout<<endl;        //delete p;        //delete vis;        //delete line;    }    return 0;}

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