c++实现凸包

#include   <iostream>           //给定点集合，求包罗所有点的最小凸包。(Jarris步进法)   

     

 #include   <fstream>             //n   为总点数，x,y是坐标。                           (即收缩法)   

 #include   <deque>                 //tx,ty是求出的逆时针凸包坐标。   

 #include   <math.h>               //坐标以0起始。   

                                                 //使用条件：   1。点可以任意给，可重复。   

 using   namespace   std;         //   2。三个以及以上的点。   

                                                 //   3。已经考虑了边上有点的情况。   

 ifstream   fin( "maxconvexpolygon.in ");   

 void   out();   

 void   go();   

 double   mytan(double   y,double   x);   

 void   in();   

 double   dist   (double   x1,double   y1,double   x2,double   y2);   

 #define   NN   1000   

 #define   pi   3.1415927   

 int   n,flag[NN];   

 double   x[NN],y[NN];   

 deque   <double>   tx,ty;   

 int   main()   

 {   

         in();   

         go();   

         out();   

         return   0;   

 }   

 void   out()   

 {   

         int   i;   

         for   (i=0;i <tx.size();i++)