四则运算

#include<stdio.h>
#include<stdlib.h>
#include<time.h>

void main(){

int a,b,n,i,j=1;
char c[5]={'/','+','-','*','/'};
srand((unsigned)time(NULL));
srand(3);
char flag;
scanf("%d",&n);//控制题目数量
for(i=1;i<=n;i++){
a=rand()%10;//随机取得一个数
flag= c[j%4];//运算符提取
j+=1;
b=rand()%10;
switch(flag){
case '+': printf("%d+%d=",a,b);printf("\n");break;
case '-': printf("%d-%d=",a,b);printf("\n");break;
case '*': printf("%d*%d=",a,b);printf("\n");break;
case '/': printf("%d/%d=",a,b);printf("\n");break;
default:
printf("error!"); break;

}

}
printf("\n");

}