第二次作业：编写一个四则运算的"软件"

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

int question_get();
int type;


void main( void ) 
{
	int r=0;
	int e=0;
	int answer;
	int n; 
	srand( (unsigned)time( NULL ) );
loop:printf( "请选择要进行测试的题目种类：" );
     printf( "\n1.加法运算\n2.减法运算\n3.乘法运算\n4.除法运算\n5.退出运算\n" );
     printf("\t\t\t请选择(1-5):");
	 scanf( "%d", &type ); 
	 
	 while( 1 )
	 {
		 int temp; 
		 int flag; 
		 answer = question_get(); 
		 printf( "请回答：\n" ); 
		 scanf( "%d", &temp ); 
		 
		 while( temp!=answer ) 
		 {
			 e++;
			 printf( "\n答案错误,再接再厉，请您重做\n" ); 
			 
			 scanf( "%d", &temp );
			 
		 }
		 r++;
		 printf( "\n恭喜你！回答正确\n" ); 
		 
		 printf( "若继续请按1，退出请按0\n" ); 
		 scanf( "%d", &flag ); 
		 
		 while( flag!=0&&flag!=1 ) 
		 {
			 printf( "按其它键无效\n" );
			 scanf( "%d", &flag ); 
		 }
		 if( flag==0 ) 
			 break; 
		 else
			 printf("您共回答了%d道题，其中正确的有%d道，错误的有%d道\n",e+r,r,e);
		 goto loop;
	 }
} 

int question_get() 
{
	int a,b,c; 
loop: if( type==1 ) 
	  { 
		  a=rand()%99;
		  b=99-a;
		  b=rand()%b;
		  printf( "%d + %d = ?", a, b ); 
		  return (a+b);
		  
	  }
	  else if( type==2 )
	  {
		  b=rand()%99;
		  c=99-b;
		  c=rand()%c;
		  printf( "%d - %d = ?", b+c, b );
		  return(c);
	  }
	  else if( type==3 )
	  {
		  a=rand()%10;
		  b=50-a; 
		  b=rand()%b; 
		  printf( "%d * %d = ?", a, b );
		  return(a*b);
	  }
	  else if( type==4 )
	  {
		  b=rand()%50;
		  c=100/b; 
		  while( 1 ) 
		  {
			  c=rand()%c;
			  if( c!=0 )
				  break;
		  }
		  printf( "%d / %d = ?", b*c, b );
		  return(c);
	  }
	  else if( type==5 )
	  {
		  printf("\t\t\t退出系统\n"); 
		  system("pause"); 
		  exit(0);
	  }
	  else if( type==0||type>5 ) 
	  {
		  printf("\t\t\t输入错误，请输入1-5内的数字\n"); 
		  printf("\t\t\t请选择(1-5):"); 
		  scanf( "%d", &type ); 
		  goto loop;
	  } 
	  
}