计算机自动出四则运算计算题（10以内）c++

计算机自动出四则运算计算题

计算机中的随机数为伪随机数，也是通过某个固定的算法算出来的。并将上一次产生的随机数作为生成下一个随机数时的输入·。C++会指定一个默认值作为随机数的种子（初始值）。由于每次运行程序中给出的种子都是同一个数值，会造成每次产生的题目都是相同的。
C++提供了设置种子的函数srand，允许在程序中设定随机数的种子。如何让每次选取的种子都不一样呢———把系统时间（time(NULL))作为种子！
程序如下：

#include <iostream>
#include <cstdlib>
#include <ctime>
using namespace std;

int main()
{
    int num1, num2, op, result1, result2;//num1,num2操作数；op：运算符
    //随机过程的实现
    srand(time(NULL));                  //随机数种子初始化
    num1 = rand() * 10 / (RAND_MAX + 1);//生成运算数
    //or num1=rand()%10;
    num2 = rand() * 10 / (RAND_MAX + 1);//生成运算数
    op = rand() * 4 / (RAND_MAX + 1);   //生成运算符 0：+，1：-，2：*，3：/
    switch (op) {
    case 0:  
        cout << num1 << "+" << num2 << "=?" << endl;
        cin >> result1;
        if (result1 == num1 + num2) cout << "You are right!" << endl;
        else cout << "You are wrong!" << endl;
        break;
    case 1:
         if (num1 < num2)
        {
            int tmp;
            tmp = num1;
            num1 = num2;
            num2 = tmp;
        }//保证减数小于被减数
        cout << num1 << "-" << num2 << "=?" << endl;
        cin >> result1;
        if (result1 == num1 - num2) cout << "You are right!" << endl;
        else cout << "You are wrong!" << endl;
        break;
    case 2: 
        cout << num1 << "*" << num2 << "=?" << endl;
        cin >> result1;
        if (result1 == num1 * num2) cout << "You are right!" << endl;
        else cout << "You are wrong!" << endl;
        break;
    case 3:
        if (num2 == 0) num2 = 1 + rand() * 9 / (RAND_MAX + 1);//防止除数为0
        cout << num1 << "/" << num2 << "=?" << endl;
        cin >> result1;
        cout << "余数为？";
        cin >> result2;
        if (result1 == num1 * num2 && result2 == num1 - num2 * result1) cout << "You are right!" << endl;
        else cout << "You are wrong!" << endl;
        break;
    }
    return 0;
}