poj 2007 Scrambled Polygon

这个题就是求凸包；

极角排序：

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#include<iostream>

#include<cstdio>

#include<cstdlib>

#include<algorithm>

#include<cmath>

#include<queue>

#include<set>

#include<map>

#include<cstring>

#include<vector>

using namespace std;

class Point

{

public:

     double x,y;    

}point[54];

int dcmp( double x )

{

   if( fabs( x ) <1.0e-8 ) return 0;

   if( x < 0 ) return -1;

   return 1;    

}

double multi( Point p1 ,Point p2 ,Point q )

{

   return ( p1.x - q.x )*( p2.y - q.y )-( p2.x - q.x )*( p1.y - q.y );     

}

double Distance( Point a , Point b )

{

   return sqrt(( a.x - b.x )*( a.x - b.x ) + ( a.y - b.y )*( a.y - b.y ));    

}

bool cmp( Point a , Point b )

{

     int t = dcmp( multi ( a , b , point[0]) );

     if( t > 0 ) return true;

     return false;

}



int main(  )

{

    int cnt = 1;

    scanf( "%lf %lf" ,&point[0].x ,&point[0].y); 

    while( scanf( "%lf %lf",&point[cnt].x,&point[cnt].y )!=EOF )

    {

        cnt++;

        while( scanf( "%lf %lf",&point[cnt].x ,&point[cnt].y ) != EOF &&(point[cnt].x||point[cnt].y))

        { 

            cnt++;

           

        }

        sort( point + 1 , point + cnt  , cmp );

        for( int i = 0 ; i < cnt ;i ++ )

         printf( "(%.0f,%.0f)\n",point[i].x,point[i].y );

        cnt = 1;

        point[0].x = 0 ; point[0].y = 0;    

    }    

    //system( "pause" );

    return 0;

}

水平排序：

View Code

#include<iostream>

#include<cstdio>

#include<cstdlib>

#include<algorithm>

#include<cmath>

#include<queue>

#include<set>

#include<map>

#include<cstring>

#include<vector>

using namespace std;

class Point

{

public:

     double x,y;    

}point[54];

int dcmp( double x )

{

   if( fabs( x ) <1.0e-8 ) return 0;

   if( x < 0 ) return -1;

   return 1;    

}

bool cmp( Point a , Point b )

{

     if( a.y == b.y ) return a.x < b.x;

     return a.y < b.y;    

}

double multi( Point p1 ,Point p2 ,Point q )

{

   return ( p1.x - q.x )*( p2.y - q.y )-( p2.x - q.x )*( p1.y - q.y );     

}

void Graham( int n )

{

   Point p[54];

   int len = 0,i; 

   for( i = 0 ; i < n ; i ++ )

   {

      while( len >= 2 && dcmp(multi( p[len-1],point[i],p[len-2] )) < 0 )    

             len --;

      p[len++] = point[i];

   }    

   int t = len + 1;

   for( i = n -2 ; i >=0 ; i --  )

   {

       while( len >= t && dcmp(multi( p[len-1],point[i],p[len-2] )) < 0 )

              len --;

       p[len++] = point[i];

   }

  

   for( i = 0 ; i < len ; i ++ )

   {

        if( dcmp( p[i].x )==0 &&dcmp( p[i].y  ) == 0 )

             break;        

   }

   len -- ;

   printf( "(0,0)\n" ); 

   t = i + 1;

   while( t != i )

   {

       printf( "(%.0f,%.0f)\n",p[t].x,p[t].y );

       t++;

       t %= len;        

   }

}

int main(  )

{

    int cnt = 1;

    scanf( "%lf %lf" ,&point[0].x ,&point[0].y); 

    while( scanf( "%lf %lf",&point[cnt].x,&point[cnt].y )!=EOF )

    {

        cnt++;

        while( scanf( "%lf %lf",&point[cnt].x ,&point[cnt].y ) != EOF &&(point[cnt].x||point[cnt].y))

        {

            cnt++;

        }

        sort( point , point + cnt  , cmp );

        Graham( cnt  );

        cnt = 1;

        point[0].x = 0 ; point[0].y = 0;    

    }    

    //system( "pause" );

    return 0;

}