C语言问题，输入两个数，运算符号随机

#include<stdio.h>
#include<stdlib.h>
int main()
{ double a1,a2,b=0;
printf("请输入两个实数\n");
scanf("%d,%d",&a1,&a2);
switch(1+rand()%4)
{
case 1: b=a1+a2;break;
case 2: b=a1-a2;break;
case 3: b=a1*a2;break;
case 4: b=a1/a2;break;
}
printf("%d\n",b);
}

这哪里错了，不懂

double a1,a2,b=0;
printf("请输入两个实数\n");
scanf("%lf,%lf",&a1,&a2);
switch(1+rand()%4)
{
case 1: b=a1+a2;printf("%lf+%lf=%.2f\n",a1,a2,b);break;
case 2: b=a1-a2;printf("%lf-%lf=%.2f\n",a1,a2,b);break;
case 3: b=a1*a2;printf("%lf*%lf=%.2f\n",a1,a2,b);break;
case 4: b=a1/a2;printf("%lf/%lf=%.2f\n",a1,a2,b);break;
}

改正一楼的二个地方就是， #include void main() { int n1,n2,result; char oper; printf("请输入两个数: "); scanf("%d%d",&n1,&n2); fflush(stdin) printf("\n请输入运算"); scanf("%c",&oper); switch(oper) { case '+': result=n1+n2; break; case '-': result=n1-n2; break; case '*': result=n1*n2; break; case '/': result=n1/n2; break; } printf("\n%d %c %d = %d\n",n1,oper,n2,result); }