1.2 借书方案知多少

#include<stdio.h>
main()
{
    int a,b,c,i=0;
    printf("A,B,C三人所选的书号分别是:\n");
    for(a=1;a<=5;a++) 
    for(b=1;b<=5;b++)
    for(c=1;c<=5;c++)
    if(a!=b&&a!=c&&c!=b)
    {
        printf("A%2d B:%2d C:%2d ",a,b,c);
        i++;
        if(i%4==0)
        printf("\n");        
    }
    printf("共有%d种有效借阅方法\n",i);
}