Convex hull seeking perimeter

1#include <iostream>2#include <cstdlib>3#include <cmath>4#include <cstdio>5 using namespacestd;6 intN;7typedefstruct8 {9     Doublex;Ten     Doubley; One }point; A  -Point p[ the],s[ the]; -  the inttop; -  - DoubleMul (Point a,point b,point c) - { +     return(b.x-a.x) * (C.Y-A.Y)-(B.Y-A.Y) * (c.x-a.x); - } +  A DoubleDis (point a,point B) at { -     returnsqrt ((a.x-b.x) * (a.x-b.x) + (A.Y-B.Y) * (a.y-b.y)); - } -  - intcmpConst void*a,Const void*b) - { inPoint c=* (Point *) A; -Point d=* (Point *) b; to     DoubleK=mul (p[0],c,d); +     if(k<0|| (!k&&dis (c,p[0]) >dis (d,p[0])))return 1; -     return-1; the } *  $ voidcon ()Panax Notoginseng { -     inti; the      for(i=1; i<n;i++) +     { A Point temp; the         if(p[i].y<p[0].y| | (p[i].y==p[0].y&&p[i].x<p[0].x)) +         { -temp=P[i]; $p[i]=p[0]; $p[0]=temp; -         } -     } theQsort (p+1, N-1,sizeof(p[0]), CMP); -s[0]=p[0];Wuyis[1]=p[1]; thes[2]=p[2]; -top=2; Wu      for(i=3; i<n;i++) -     { About          while(top>=2&&mul (s[top-1],s[top],p[i]) <=0) top--; $top++; -s[top]=P[i]; -     } - } A  + intMain () the { -      while(cin>>n,n) $     { the         inti; the          for(i=0; i<n;i++) the         { theCin>>p[i].x>>p[i].y; -         } in         if(n==1) the         { thecout<<"0.00"<<Endl; About             Continue; the         } the         Else if(n==2) the         { +printf"%.2f\n", Dis (p[0],p[1])); -             Continue; the         }Bayi con (); the         Doublecoun=0; the          for(i=0; i<top;i++) -         { -Coun+=dis (s[i],s[i+1]); the         } theCoun+=dis (s[top],s[0]); theprintf"%.2f\n", Coun); the     } -     return 0; the}

Convex hull seeking perimeter