软件工程课后作业3：扩展：真分数运算

编程代码：
#include<iostream>
#include<ctime>
using namespace std;
 
void exchange(int &a, int &b)          
{
     int temp = a;
     a = b;
     b = temp;
 }
 
 void main()
 {
     srand((int)time(NULL));            
     int num1, num2,num3,snum,snum1;    
     double result;                     
     char symbol[4];                    
     symbol[0] = '+';
     symbol[1] = '-';
     symbol[2] = '*';
     symbol[3] = '/';
     for (int sexp=0; sexp < 20;sexp++)
     {
         num1 = rand() % 100;
         num2 = rand() % 100;
         snum = rand() % 4;
         if (num2 == 0 && snum == 3)    
             break;
         switch (snum)
         {
         case 0:result = num1 + num2; break;
         case 1:result = num1 - num2; break;
         case 2:result = num1 * num2; break;
         case 3:double dnum1 = (int)num1; double dnum2 = (int)num2; result = dnum1 / dnum2; break;  //将除的结果显示为double型
         }
         cout << num1 << symbol[snum] << num2 << "="<<result<<endl;
     }
     for (int fexp = 0; fexp < 10; fexp++)   
     {
         num1 = rand() % 100;
         num2 = rand() % 100;
         num3 = rand() % 100;
         snum = rand() % 4;
         snum1 = rand() % 4;
         if ((num2 == 0 && snum == 3)||(num3==0&&snum1==3))      
             continue;
         if (snum == 3 && num1 > num2)     
             exchange(num1,num2);
         if (snum1 == 3 && num2 > num3)
             exchange(num2, num3);
         cout << num1 << symbol[snum] << num2 <<symbol[snum1]<<num3<< "="<< endl;
     }
     system("pause");
 }