POJ 1696 Space Ant

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题目大意：

有M组样例

每组样例N个点

每个点为 编号 X  Y

每天只能左转移动一点

求点的编号顺序

 

思路：

从x最小的点对应在y轴上的投影为起点

做卷包裹法不返回起点即可

每添加一点标记下

直到所有点都走完

 

#include <cmath>#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const double eps=1e-7;//精度const int INF=1<<29;struct Point{double x,y;Point(double x=0,double y=0):x(x),y(y){}};typedef Point Vector;Vector operator+(Vector a,Vector b){return Vector(a.x+b.x,a.y+b.y);}//向量+向量=向量Vector operator-(Point a,Point b){return Vector(a.x-b.x,a.y-b.y);}//点-点=向量Vector operator*(Vector a,double p){return Vector(a.x*p,a.y*p);}//向量*实数=向量Vector operator/(Vector a,double p){return Vector(a.x/p,a.y/p);}//向量/实数=向量bool operator<(const Point&a,const Point&b){return a.x<b.x||(a.x==b.x&&a.y<b.y);}int doublecmp(double x){//判断double等于0或。。。if(fabs(x)<eps)return 0;else return x<0?-1:1;}bool operator==(const Point&a,const Point&b){return doublecmp(a.x-b.x)==0&&doublecmp(a.y-b.y)==0;}double Dot(Vector a,Vector b){return a.x*b.x+a.y*b.y;}//|a|*|b|*cosθ 点积double Length(Vector a){return sqrt(Dot(a,a));}//|a| 向量长度double Angle(Vector a,Vector b){return acos(Dot(a,b)/Length(a)/Length(b));}//向量夹角θdouble Cross(Vector a,Vector b){return a.x*b.y-a.y*b.x;}//叉积 向量围成的平行四边形的面积double Area2(Point a,Point b,Point c){return Cross(b-a,c-a);}//同上 参数为三个点Vector Rotate(Vector a,double rad){//向量旋转rad弧度return Vector(a.x*cos(rad)-a.y*sin(rad),a.x*sin(rad)+a.y*cos(rad));}Vector Normal(Vector a){//计算单位法线double L=Length(a);return Vector(-a.y/L,a.x/L);}Point GetLineProjection(Point p,Point a,Point b){Vector v=b-a;return a+v*(Dot(v,p-a)/Dot(v,v));}Point GetLineIntersection(Point p,Vector v,Point q,Vector w){//求直线交点 有唯一交点时可用Vector u=p-q;double t=Cross(w,u)/Cross(v,w);return p+v*t;}//直线P+tV//--------------------------------------int vis[55];struct node{int pos;Point p;bool friend operator<(node a,node b){return a.p<b.p;}}arr[55];int main(){int T;scanf("%d",&T);while(T--){int n;scanf("%d",&n);printf("%d",n);double star=INF;arr[0].pos=0;for(int i=1;i<=n;i++){arr[i].pos=0;scanf("%*d%lf%lf",&arr[i].p.x,&arr[i].p.y);star=min(star,arr[i].p.y);}arr[0].p.x=0;arr[0].p.y=star;int count=1;Vector curv(1,0);Point curp=arr[0].p;while(count<=n){double minjiao=INF;double mindis=INF;int purpose=-1;for(int i=1;i<=n;i++)if(!arr[i].pos){double jiao=Angle(curv,arr[i].p-curp);double dis=Length(arr[i].p-curp);if(jiao<minjiao||(doublecmp(jiao-minjiao)==0&&dis<mindis)){mindis=dis;minjiao=jiao;purpose=i;}}curv=arr[purpose].p-curp;curp=arr[purpose].p;arr[purpose].pos=count++;}for(int i=1;i<=n;i++)for(int j=1;j<=n;j++)if(arr[j].pos==i)printf(" %d",j);printf("\n");}return 0;}