关于运用c语言出30道不重复的四则运算

#include<stdio.h>
#include<stdlib.h>
#include <time.h>
#define N 30
main()
{
int a,b,k,i,n;
float c,d;
srand(time(NULL));
do{
printf("\n请输入数字类型(1.整数) -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;
}
}while(n!=-1);
}