凸包问题求解 使用蛮力算法

 /*****************************************************/
/*                                                   */
/*       凸包问题求解                                */
/*       使用蛮力算法                                */
/*       Author:lixiongwei                           */
/*       Time:06/12/11 Sun.                          */
/*       WIN XP+(TC/Win_TC/VC++6.0)                  */
/*                                                   */
/*****************************************************/
#include <stdio.h>
#include <conio.h>
#include <time.h>
#include <stdlib.h>
#include <graphics.h>
#define MAX_X   630
#define MAX_Y   470
#define MAX_NUM  200
/******************函数原型以及变量类型声明***********************/
struct  point{
    double x; /*横坐标*/
    double y; /*纵坐标*/
    int flag; /*标记凸点*/
};
struct point my_point[MAX_NUM]; /*定义凸包点的信息*/
void my_graphics();
void my_convex_hull();
/*****************************主函数******************************/
int main()
{
    int i,j,k;
    clock_t   start,end;  
    double   elapsed,temp_x,temp_y;

    /*初始化随机数*/
    srand( (unsigned)time( NULL ) );
    start=clock();
    for(i=0;i<MAX_NUM;i++)
    {
      while( (my_point[i].x = (rand() % MAX_X))<10 );/*随机产生横坐标*/
      while( (my_point[i].y = (rand() % MAX_Y))<10 );/*随机产生纵坐标*/
      my_point[i].flag=0;
    }
    /**********************************/
    for(i=0;i<MAX_NUM;i++)
        printf("my_point[%d].x=%f    my_point[%d].y=%f    my_point[%d].flag=%d/n",
               i,my_point[i].x,i,my_point[i].y,i,my_point[i].flag);

    printf("/nNow compute,press any key to continue.../n");
    getch();
    my_convex_hull();/*调用凸包计算函数*/
    for(i=0;i<MAX_NUM;i++)
        printf("my_point[%d].x=%f    my_point[%d].y=%f    my_point[%d].flag=%d/n",
               i,my_point[i].x,   i,my_point[i].y,   i,my_point[i].flag);

    printf("/nPress any key to watch screen.../n");
    getch();
    my_graphics();
    end=clock();
    elapsed=((double)(end-start))/CLK_TCK;
    printf("This program use time: %fs. goodbye everyone~!/n",elapsed);
    getch();
    return 0;
}

/******************使用蛮力算法求凸包计算函数的定义*******************/
void  my_convex_hull()
{
    int i,j,k,sign=0;
    double a=0,b=0,c=0;

    for(i=0; i<MAX_NUM; ++i)
        for(j=i+1; j<MAX_NUM; ++j)
        {
             a = my_point[j].y - my_point[i].y;
             b = my_point[i].x - my_point[j].x;
             c = ( my_point[i].x * my_point[j].y )-( my_point[i].y * my_point[j].x );

             sign=0;
             for(k=0; k<MAX_NUM; ++k)
             {
                 if( (k==j)||(k==i) )
                     continue;
                 /*
                 if( ( a*my_point[k].x+b*my_point[k].y ) == c)
                     exit(1);
                 */   /*如果有两个以上的点共线，不处理*/

                 if( ( (a*(my_point[k].x)+b*(my_point[k].y))>c ) )
                     ++sign;
                 if( ( (a*(my_point[k].x)+b*(my_point[k].y))<c ) )
                     --sign;

              }/*end inside for*/

              if( (sign==(MAX_NUM-2))||((sign==(2-MAX_NUM))) )
              {
                   printf("/n/n");
                   my_point[i].flag=1;
                   my_point[j].flag=1;
              }

         }/*inside for end */

        printf("/n/n");
}

/******************屏幕输出函数的函数定义*******************/
void my_graphics()
{
    int i,j,k,convex_hull,sign;
    double a=0,b=0,c=0;
    struct point border_point[MAX_NUM]; /*记录边界凸点*/
    int graphdriver=VGA;
    int graphmode=VGAHI;

    initgraph(&graphdriver,&graphmode,"");
    cleardevice();
    setcolor(WHITE);
    rectangle(0,0,639,479);
    rectangle(2,2,637,477);

    for(i=0,j=0;i<MAX_NUM;i++)
    {
        if(my_point[i].flag==1)
        {
            border_point[j].x = my_point[i].x;
            border_point[j].y = my_point[i].y;
            border_point[j].flag = 1;
            ++j;
         }
    }
    convex_hull=j;/*记录顶点个数*/

    for(i=0;i<MAX_NUM;++i)
    {
        if(my_point[i].flag==1)
        {
            setcolor(YELLOW);
            fillellipse(my_point[i].x, my_point[i].y, 3,3);
         }
        else
        {
            setcolor(WHITE);
            circle(my_point[i].x, my_point[i].y ,2);
        }
    }

    /***********以下连接各个凸点*************/
    setcolor(WHITE);
    for(i=0; i<convex_hull; ++i)
        for(j=i+1; j<convex_hull; ++j)
        {
             a = border_point[j].y - border_point[i].y;
             b = border_point[i].x - border_point[j].x;
             c = ( border_point[i].x * border_point[j].y )-( border_point[i].y * border_point[j].x );

             sign=0;
             for(k=0; k<convex_hull; ++k)
             {
                 if( (k==j)||(k==i) )
                     continue;
                 if( ( (a*(border_point[k].x)+b*(border_point[k].y))>c ) )
                     ++sign;
                 if( ( (a*(border_point[k].x)+b*(border_point[k].y))<c ) )
                     --sign;

              }/*end inside for*/

              if( (sign==(convex_hull-2))||((sign==(2-convex_hull))) )
              {
                   line(border_point[i].x,border_point[i].y,border_point[j].x,border_point[j].y);

              }

         }/*inside for end */
    /**************************/

    getch();
    closegraph();
}