#include<stdio.h>
#include<time.h>
#include<stdlib.h>
main()
{
    int i,j,lep,leg;
    int count=0;
    int nut=0;
    char ch;
    char str[7][10]={"abcdefghi","jklmnopqr","stuvwxyz","ABCDEFGHI","JKLMNOPQR","STUVWXYZ0","123456789"};

    srand((unsigned)time(NULL));

    for(i=0;i<7;i++)
    {
        for(j=0;j<10;j++)
        {
            lep=rand()%10;
            leg=rand()%7;
            ch=str[i][lep];
            str[i][lep]=str[leg][j];
            str[leg][j]=ch;
        }
    }

    while(1)
    {
        nut=0;
        while(1)
        {
            lep=rand()%10;
            leg=rand()%7;
            if(str[leg][lep]!=' ' && str[leg][lep]!='\0')  
            {
                printf("%c",str[leg][lep]);               
                nut++;                                    
            }
            if(nut==4)break;
        }
        ++count;

        if(count!=4)
        {
            printf("-");
        }

        if(count==4)
        {
            break;   
        }
    }
    printf("\n");
  
}

#include<stdio.h>
#include<conio.h>
#include<time.h>
#include<stdlib.h>
main()
{
    char str[7][10]={"abcdefghi","jklmnopqr","stuvwxyz","ABCDEFGHI","JKLMNOPQR","STUVWXYZ0","123456789"};

    srand((unsigned)time(NULL));

    for (int i=0;i<16;i++)
    {
        int h=rand()%7;
        int l=rand()%9;
        printf("%c",str[h][l]);
        if ((i+1)%4==0&&(i+1)!=16)
            printf("-");
    }
    printf("\n");
    getch();
} 

随便写写

用随机函数rand不是很简单？