跳动的小球_C/C++

#include <graphics.h>
#include <stdlib.h>
#include <stdio.h>
#include <conio.h>
#include <math.h>
#define ESC 0x1b;
#define MAXNUM 100 main()
{   char *buf;
    char sign,sign1[MAXNUM] = {1},sign2[MAXNUM] = {1};
    int i,size,a;
    int x[MAXNUM],y[MAXNUM],r[MAXNUM][MAXNUM];
    int gd = DETECT,gm;
    clrscr();
    printf("please input the number of ball you want:\n");
    scanf("%d",&a);
    registerbgidriver(EGAVGA_driver);
    initgraph(&gd,&gm,"");
    setcolor(YELLOW);
    setfillstyle(SOLID_FILL,9);
    rectangle(0,0,getmaxx(),getmaxy());
    rectangle(1,1,getmaxx()-1,getmaxy()-1);
    bar(2,2,getmaxx()-2,getmaxy()-2);
    for(i = 8;i >=0;i --)
    {   setcolor(i + 7);
circle(11,getmaxy() - 11,i);
    }
    size = imagesize(2,getmaxy() - 20,20,getmaxy() - 2);
    buf = malloc(size);
    getimage(2,getmaxy()-20,20,getmaxy() - 2,buf);
    for(i = 8;i >= 0;i --)
    {   setcolor(9);
circle(11,getmaxy() - 11,i);
    }
    randomize();
    for(i = 0;i < a;i ++)
    {   x[i] = random(600) + 20;
y[i] = random(400) + 32;
    }     while(1)
    {   if(kbhit())
    {   sign = getch();
        if(sign == 0x1b)
    {   free(buf);
        break;
    }
    }
else
    {
        for(i = 0;i < a;i ++){
        putimage((sign1[i] == 1 ? x[i] ++ : x[i] --),
   (sign2[i] == 1 ? y[i] ++ : y[i] --),buf,COPY_PUT);         if(x[i] > getmaxx() - 21)
    sign1[i] = 0;
        if(x[i] < 3) sign1[i] = 1;
        if(y[i] > getmaxy() - 21)
    sign2[i] = 0;
        if(y[i] < 3) sign2[i] = 1;}
    }
    }
    free(buf);
    closegraph();
    return 0;
} right">（出处：清风软件下载学院）