求一个随机生成迷宫的算法~

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#define N 22
void makeline(int a[][N],int x1,int y1,int x2,int y2)
{//产生直线路径
    int xs=x2-x1,ys=y2-y1;
    double k,w1,w2;
    k=(double)ys/((double)xs+0.00001);
    xs=xs<0?-1:(xs>0?1:xs);
    ys=ys<0?-1:(ys>0?1:ys);
    while(x1!=x2||y1!=y2)
    {
        a[x1][y1]=0;
        if(xs&&ys)
        {
            w1=k-(y2-y1)/((double)(x2-x1-xs)+0.00001);
            w2=k-(y2-y1-ys)/((double)(x2-x1)+0.00001);
            if(w1<0)w1=-w1;
            if(w2<0)w2=-w2;
            if(w1<w2)x1+=xs;
            else y1+=ys;
        }
        else
        {
            if(xs)x1+=xs;
            else y1+=ys;
        }
    }
    a[x1][y1]=0;   
}
void makepath(int a[][N])
{
    //产生随机路径
    int i,j,k,x1,x2,y1,y2;
    for(i=0; i<N; i++)
    {
        for(j=0; j<N; j++)
        {
            k=rand()%1000;
            if(k>100&&k<350&&i>0&&i<N-1&&j>0&&j<N-1)a[i][j]=0;  //产生随机点
            else a[i][j]=1;
        }
    }
    x1=x2=y1=y2=1;
    for(i=0;i<12;i++)
    {
        x2=rand()%(N-2)+1;
        y2=rand()%(N-2)+1;
        makeline(a,x1,y1,x2,y2);    //产生12根随机直线,第一根线起点是入口，最后一根线终点在出口
        x1=x2;
        y1=y2;
    }
    x2=y2=N-2;
    makeline(a,x1,y1,x2,y2);      
    a[1][0]='I';
    a[N-2][N-1]='O';
}
int main()
{
    int a[N][N];
    int i,j;
    srand((unsigned)time(NULL));
    makepath(a);
    for(i=0; i<N; i++)
    {
        for(j=0; j<N; j++)
        {
            if(a[i][j]>32)printf("%c%c",a[i][j],a[i][j]);
            else if(a[i][j])printf("■");
            else printf("  ");
        }
        printf("\n");
    }
    return 0;
}