四则运算1

四则运算支持整数和真分数
 1 #include <iostream>
 2 #include <ctime>
 3 #include <cstdlib>
 4 #include <string>
 5 #include <iomanip>
 6 #include <sstream>
 7 using namespace std;
 8 
 9 bool isTrueFraction(int numerator,int denominator)    //判断产生的分数是否是真分数
10 {
11     if(numerator >= denominator)
12         return false;
13 
14     for(int i = 2 ; i <= numerator ; i++)      //判断分数是否能够约分
15     {
16         if(numerator % i ==0 && denominator % i ==0)
17             return false;
18     }
19 
20     return true;
21 }
22 
23 string getNum()
24 {
25     int n = rand();
26     if(n%7 == 0)       //若随机数n是7的倍数，产生一个真分数和一个整数，否则为两个整数
27     {
28         int num1 = rand() % 100;
29         int num2 = rand() % 100;
30         int num3 = rand() % 100;
31        // cout << num1 <<"+"<<num2<<"+"<<num3<<endl;
32         if(isTrueFraction(num1,num2))
33         {
34             stringstream s1,s2,s3;
35             string ss1,ss2,ss3;
36             s1<<num1;
37             s1>>ss1;
38             s2<<num2;
39             s2>>ss2;
40             s3<<num3;
41             s3>>ss3;
42             return ss1+"/"+ss2+","+ss3;
43         }else
44         {
45             return getNum();
46         }
47     }else
48     {
49         int num1 = rand() % 100;
50         int num2 = rand() % 100;
51         //cout << num1 <<"+"<<num2<<endl;
52         stringstream s1,s2;
53         string ss1,ss2;
54         s1<<num1;
55         s1>>ss1;
56         s2<<num2;
57         s2>>ss2;
58         return ss1+","+ss2;
59     }
60 }
61 
62 char getOperator(string num2)
63 {
64     char a[] = {'+','-','*','/'};
65     if(num2 == "0")
66         return a[rand() % 3];
67     else
68         return a[rand() % 4];
69 
70 }
71 
72 
73 int main(int argc, char *argv[])
74 {
75     srand((int)time(0));
76 
77     for(int i = 0; i < 30 ; i++){
78         string num = getNum();
79         string num1 = num.substr(0,num.find(","));  //由逗号分割，
80         string num2 = num.substr(num.find(",")+1);
81         char op = getOperator(num2);
82         cout <<left << setw(4) << i+1 << setw(5)<<num1 <<setw(2)<<op<<setw(5)<<num2 <<endl;
83     }
84 
85     return 0;
86 }



首先 getNum()获得两个数，并用逗号分隔的字符串格式返回，通过string::find()和string::substr()分别获得两个运算数，
然后 通过getOperator()获得运算符，并以第二个数作为参数，如果第二个数为0，那么不能取除法，
最后 附上运行截图。