随机生成四则运算法则

#include<stdio.h>
#include<stdlib.h>
#include <time.h>
#define N 30
void main()
{
    int a,b,k,i,n;
    double c,d;
    srand(time(NULL));
    do{
        printf("\n请输入数字类型(1.整数 2.小数) -1为退出程序: ");
        scanf("%d",&n);

        switch(n)
        {
              case 1；
                  {
                    for(i=0;i<N;i++)
                    {
                        a=rand()%100+1;
                        b=rand()%100+1;
                        k=rand()%4+1;
                        printf("%d",a);
                        switch(k)
                        {
                                case 1:printf("+");break;
                                case 2:printf("-");break;
                                case 3:printf("*");break;
                                case 4:printf("/");break;
                        }
                        printf("%d=\t\t",b);
                    }
                    break;
                }
                break;
              case 2:
                  {
                      for(i=0;i<N;i++)
                      {
                          c=rand()*0.001+1;
                          d=rand()*0.001+1;
                          k=rand()%4+1;
                          printf("%0.2f",c);
                          switch(k)
                          {
                          case 1:printf("+");break;
                          case 2:printf("-");break;
                          case 3:printf("*");break;
                          case 4:printf("/");break;
                          }
                          printf("%0.2f=\t",d);
                      }
                      break;
                  }
                  break;
        }
    }
    while(n!=-1);
}