算法思想：

算法思想：
(1) 產生兩個隨機數
(2) 產生一個運算符
(3) 用戶輸入答案
(4) 驗證答案正確與否
(5) 轉(1) 重複執行

主函數中用到了srand(time(NULL))上百度查了一下和隨機產生有關。如果在程序運行時沒有自主設置種子的話，用函數rand產生的隨機數序列會是一樣的。
而用srand設置隨機數種子後，可能產生不同的隨機序列（概率很大）。

[cpp] view plaincopyprint?

int main()  

{  

    int number = 2;  

    int choice;  

    srand(time(NULL));  

  

    do  

    {  

        ShowMenu();  

        choice = getchar();  

        getchar(); //清除行尾回車   

        switch(choice)  

        {  

        case '1':  

        case '2':  

        case '3':  

        case '4':  

        case '5':  

            Arithmetic(choice,number);  

            break;  

        case '6':  

            cout<<"輸入題目數:";  

            cin>>number;  

            getchar();  

        }  

 }  


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

}  

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

    do
    {
        ShowMenu();
        choice = getchar();
        getchar(); //清除行尾回車
        switch(choice)
        {
        case '1':
        case '2':
        case '3':
        case '4':
        case '5':
            Arithmetic(choice,number);
            break;
        case '6':
            cout<<"輸入題目數:";
            cin>>number;
            getchar();
        }
    }
    while(choice!='0');
    return 0;
}

主函數中調用了兩個函數：菜單函數ShowMenu和四則運算函數Arithmetic。

菜單函數

void ShowMenu()
{
    cout<<"***********************"<<endl;
    cout<<"*     1- 加法         *"<<endl;
    cout<<"*     2- 減法         *"<<endl;
    cout<<"*     3- 乘法         *"<<endl;
    cout<<"*     4- 除法         *"<<endl;
    cout<<"*     5- 混合運算     *"<<endl;
    cout<<"*     6- 設置題目數   *"<<endl;
    cout<<"*     0- 退出         *"<<endl;
    cout<<"***********************"<<endl;
}

void ShowMenu()
{
    cout<<"***********************"<<endl;
    cout<<"*     1- 加法         *"<<endl;
    cout<<"*     2- 減法         *"<<endl;
    cout<<"*     3- 乘法         *"<<endl;
    cout<<"*     4- 除法         *"<<endl;
    cout<<"*     5- 混合運算     *"<<endl;
    cout<<"*     6- 設置題目數   *"<<endl;
    cout<<"*     0- 退出         *"<<endl;
    cout<<"***********************"<<endl;
}

四則運算函數中用了隨機產生rand()%101。 rand()是隨機取一個整數，再摸101，就是取餘數。合起來的意思就是在0-100的範圍內隨機取一個整數。

運用循環控制題目次數。

void Arithmetic(int kind,int number)
{
    int i;
    int answer,result;
    char str[80];
    int score=0;
    int operand1,operand2,operator1;
    cout<<"四則運算,題目數:"<<number<<endl;
    for(i=0; i<number; i++)//控制程序的題目數
    {
        operand1 =rand()%101;//產生1到100內的隨機數
        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爲1到5之間的隨機數
        }
        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) //注意除數爲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<<"按任意鍵返回！";
    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<<"四則運算,題目數:"<<number<<endl;
    for(i=0; i<number; i++)//控制程序的題目數
    {
        operand1 =rand()%101;//產生1到100內的隨機數
        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爲1到5之間的隨機數
        }
        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) //注意除數爲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<<"按任意鍵返回！";
    getch();
    cout<<endl;
}

再加上相應的頭文件

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