算法思想：

算法思想：
(1) 产生两个随机数
(2) 产生一个运算符
(3) 用户输入答案
(4) 验证答案正确与否
(5) 转(1) 重复执行

主函数中用到了srand(time(NULL))上百度查了一下和随机产生有关。如果在程序运行时没有自主设置种子的话，用函数rand产生的随机数序列会是一样的。
而用srand设置随机数种子后，可能产生不同的随机序列（概率很大）。

[cpp] view plaincopyprint?

int main()  

{  

    int number = 2;  

    int choice;  

    srand(time(NULL));  

  

    do  

    {  

        ShowMenu();  

        choice = getchar();  

        getchar(); //清除行尾回车   

        switch(choice)  

        {  

        case '1':  

        case '2':  

        case '3':  

        case '4':  

        case '5':  

            Arithmetic(choice,number);  

            break;  

        case '6':  

            cout<<"输入题目数:";  

            cin>>number;  

            getchar();  

        }  

 }  


    while(choice!='0');      return 0;

}  

int main()
{
    int number = 2;
    int choice;
    srand(time(NULL));

    do
    {
        ShowMenu();
        choice = getchar();
        getchar(); //清除行尾回车
        switch(choice)
        {
        case '1':
        case '2':
        case '3':
        case '4':
        case '5':
            Arithmetic(choice,number);
            break;
        case '6':
            cout<<"输入题目数:";
            cin>>number;
            getchar();
        }
    }
    while(choice!='0');
    return 0;
}

主函数中调用了两个函数：菜单函数ShowMenu和四则运算函数Arithmetic。

菜单函数

void ShowMenu()
{
    cout<<"***********************"<<endl;
    cout<<"*     1- 加法         *"<<endl;
    cout<<"*     2- 减法         *"<<endl;
    cout<<"*     3- 乘法         *"<<endl;
    cout<<"*     4- 除法         *"<<endl;
    cout<<"*     5- 混合运算     *"<<endl;
    cout<<"*     6- 设置题目数   *"<<endl;
    cout<<"*     0- 退出         *"<<endl;
    cout<<"***********************"<<endl;
}

void ShowMenu()
{
    cout<<"***********************"<<endl;
    cout<<"*     1- 加法         *"<<endl;
    cout<<"*     2- 减法         *"<<endl;
    cout<<"*     3- 乘法         *"<<endl;
    cout<<"*     4- 除法         *"<<endl;
    cout<<"*     5- 混合运算     *"<<endl;
    cout<<"*     6- 设置题目数   *"<<endl;
    cout<<"*     0- 退出         *"<<endl;
    cout<<"***********************"<<endl;
}

四则运算函数中用了随机产生rand()%101。 rand()是随机取一个整数，再摸101，就是取余数。合起来的意思就是在0-100的范围内随机取一个整数。

运用循环控制题目次数。

void Arithmetic(int kind,int number)
{
    int i;
    int answer,result;
    char str[80];
    int score=0;
    int operand1,operand2,operator1;
    cout<<"四则运算,题目数:"<<number<<endl;
    for(i=0; i<number; i++)//控制程序的题目数
    {
        operand1 =rand()%101;//产生1到100内的随机数
        operand2 =rand()%101;
        switch(kind)
        {
        case '1':
            operator1=1;
            break;
        case '2':
            operator1=2;
            break;
        case '3':
            operator1=3;
            break;
        case '4':
            operator1=4;
            break;
        default:
            operator1=rand()%4+1;//operator1为1到5之间的随机数
        }
        switch(operator1)
        {
        case 1:
            cout<<operand1<<"+"<<operand2<<"=";
            result =operand1+operand2;
            break;
        case 2:
            cout<<operand1<<"-"<<operand2<<"=";
            result =operand1-operand2;
            break;
        case 3:
            cout<<operand1<<"*"<<operand2<<"=";
            result =operand1*operand2;
            break;
        case 4:
            if(operand2==0) //注意除数为0
                operand2=1;
            operand1 = operand1 * operand2;
            cout<<operand1<<"/"<<operand2<<"=";
            result =operand1/operand2;
        }
        //cin>>answer;
        cin.getline(str,80);
        //answer = atoi(str);
        sscanf(str,"%d",&answer);
        if(answer==result)
            score+=10;
    }
    cout<<"您的得分:"<<score<<endl;
    cout<<"按任意键返回！";
    getch();
    cout<<endl;
}

void Arithmetic(int kind,int number)
{
    int i;
    int answer,result;
    char str[80];
    int score=0;
    int operand1,operand2,operator1;
    cout<<"四则运算,题目数:"<<number<<endl;
    for(i=0; i<number; i++)//控制程序的题目数
    {
        operand1 =rand()%101;//产生1到100内的随机数
        operand2 =rand()%101;
        switch(kind)
        {
        case '1':
            operator1=1;
            break;
        case '2':
            operator1=2;
            break;
        case '3':
            operator1=3;
            break;
        case '4':
            operator1=4;
            break;
        default:
            operator1=rand()%4+1;//operator1为1到5之间的随机数
        }
        switch(operator1)
        {
        case 1:
            cout<<operand1<<"+"<<operand2<<"=";
            result =operand1+operand2;
            break;
        case 2:
            cout<<operand1<<"-"<<operand2<<"=";
            result =operand1-operand2;
            break;
        case 3:
            cout<<operand1<<"*"<<operand2<<"=";
            result =operand1*operand2;
            break;
        case 4:
            if(operand2==0) //注意除数为0
				operand2=1;
			operand1 = operand1 * operand2;
            cout<<operand1<<"/"<<operand2<<"=";
            result =operand1/operand2;
        }
        //cin>>answer;
        cin.getline(str,80);
        //answer = atoi(str);
        sscanf(str,"%d",&answer);
        if(answer==result)
            score+=10;
    }
    cout<<"您的得分:"<<score<<endl;
    cout<<"按任意键返回！";
    getch();
    cout<<endl;
}

再加上相应的头文件

#include <iostream>
#include <time.h>
#include <stdlib.h>
#include <conio.h>
using namespace std;