2015年ALPC暑期专题练习I （计算几何） Space Ant

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开始用求凸包的方法做的代码。
#include<iostream>#include<cstring>#include<cstdlib>#include<cstdio>#include<string>#include<map>#include<set>#include<algorithm>#include<vector>#include<stack>#include<queue>#include<cmath>using namespace std;/*********************************************************************/const int MAX_NUM = 50+10;struct plant{  int id,x,y;  double cos;}p[MAX_NUM];int sk[MAX_NUM],skLen;double GetCosWithX (plant& a, plant& b){return (b.x-a.x) / sqrt( pow(a.x-b.x,2)+pow(a.y-b.y,2) );}double min_2 (int x,int y) {return x<y?x:y;}int CrossMuti (plant a,plant b){return a.x*b.y-a.y*b.x;}bool cmpPlant (plant a,plant b){  if (a.cos>b.cos)return true;  else if (a.cos==b.cos)return a.x<=b.x&&a.y<=b.y;  elsereturn false;}void HandleStack (int i){  if (skLen<=3){sk[skLen++]=i;return;  }  plant ab,bc;  while (1)  {if (skLen<2){printf ("handle error\n");return;}ab.x=p[sk[skLen-1]].x-p[sk[skLen-2]].x;ab.y=p[sk[skLen-1]].y-p[sk[skLen-2]].y;bc.x=p[i].x-p[sk[skLen-1]].x;bc.y=p[i].y-p[sk[skLen-1]].y;if (CrossMuti(ab,bc)>=0){  sk[skLen++]=i;  return;}else  --skLen;  }}/*********************************************************************/int main(){  int t,n;  scanf ("%d",&t);  while (t--)  {scanf ("%d",&n);int minY=1000,minX=1000,minID;//set<point,int>for (int i=0;i<n;i++){  scanf ("%d%d%d",&p[i].id,&p[i].x,&p[i].y);  if (minY>p[i].y){minY=p[i].y;minX=p[i].x;minID=i;  }  else if (minY==p[i].y && minX>p[i].x){minX=p[i].x;minID=i;  }}p[minID].cos=1.0;for (int i=0;i<n;i++){  if (i==minID) continue;  p[i].cos=GetCosWithX (p[minID],p[i]);}sort (p,p+n,cmpPlant);/*for (int i=0;i<n;i++)  printf ("%d ",p[i].id);printf ("\n");*/skLen=0;sk[skLen++]=0;for (int i=1;i<n;i++){  HandleStack (i);  /*for (int j=0;j<skLen;j++)printf ("%d ",p[sk[j]].id);printf ("\n");*/}for (int j=0;j<skLen;j++)  printf ("%d ",p[sk[j]].id);printf ("\n");  }  return 0;}
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