/*
rand()函數(shù)用法：（轉載） 
1、rand()不需要參數(shù)，它會返回一個從0到最大隨機數(shù)的任意整數(shù)，最大隨機數(shù)的大小通常是固定的一個大整數(shù)。
2、如果你要產(chǎn)生0~99這100個整數(shù)中的一個隨機整數(shù)，可以表達為：int num = rand() % 100; 
這樣，num的值就是一個0~99中的一個隨機數(shù)了。
3、如果要產(chǎn)生1~100，則是這樣：int num = rand() % 100 + 1;
4、總結來說，可以表示為：int num = rand() % n +a;
其中的a是起始值，n-1+a是終止值，n是整數(shù)的范圍。
5、一般性：rand() % (b-a+1)+ a ; 就表示 a~b 之間的一個隨機整數(shù)。
6、若要產(chǎn)生0-1之間的小數(shù)，則可以先取得0-10的整數(shù)，然后均除以10即可得到“隨機到十分位”的10個隨機小數(shù)。
若要得到“隨機到百分位”的隨機小數(shù)，則需要先得到0~100的10個整數(shù)，然后均除以100，其它情況依 此類推。
*/
#include<iostream>
#include<cmath>
#include <stdlib.h>
using namespace std;
int main()
{
	int x,y,a;  //x和y是兩個隨機生成的數(shù)，a為學生輸入的答案 
	int sum=0;  //sum是兩個數(shù)相乘的結果
	int count=0;//count為計數(shù)器 
	int right=0;//記錄對的題數(shù)
	float s;    //計算正確率 
	do
	{
		count++;
		x=rand()%10;//隨機數(shù) 
		y=rand()%10;
		sum=x*y;
		cout << x << " * " << y << " = " << endl;
		cout << "Please enter the answer :" << endl;
		cin >> a;
		if(a==sum)
		{
			right++; 
			switch(rand()%4)
			{
				case 0:	cout << "Very good!" << endl << endl;break;
				case 1:	cout << "Excellent!" << endl << endl;break;
				case 2:	cout << "Nice work!" << endl << endl;break;
				case 3:	cout << "Keep up the good work!" << endl << endl;break;
			}
		}
		else
		{
			switch(rand()%4)
			{	
				case 0:	cout << "No. Please try again." << endl << endl;break;
				case 1:	cout << "Wrong. Try once more." << endl << endl;break;
				case 2:	cout << "Don't give up!" << endl << endl;break;
				case 3:	cout << "No. Keep trying." << endl << endl;break;
			}
		}
	}while(count<10);
	s=right*1.0/count;//計算正確率 
	if(s<0.75)
	{
		cout <<"Please ask your instructor foe extra help" << endl;
	}
	return 0;
}

#include<iostream>
#include<cmath>
#include <stdlib.h>
using namespace std;
int main()
{
	int x,y,a;  //x和y是兩個隨機生成的數(shù)，a為學生輸入的答案 
	int sum=0;  //sum是兩個數(shù)相乘的結果
	int count=0;//count為計數(shù)器 
	int right=0;//記錄對的題數(shù)
	float s;    //計算正確率 
	int note=0;//記錄能力等級 
	int f=0;//記錄用戶所希望學的問題 
	cout << "Please enter your ability level, 1 or 2" << endl;
	cin >> note; 
	cout << endl;
	cout << "************" << endl;
	cout << "*1:加法問題*" << endl; 
	cout << "*2:減法問題*" << endl; 
	cout << "*3:乘法問題*" << endl;
	cout << "*4:除法問題*" << endl;
	cout << "************" << endl;
	cout << "Please enter the type of arithmetic problem you want to learn" << endl;
	cin >> f;
	do
	{
	        count++;
		if(note==1)
		{			
			x=rand()%10;//隨機數(shù) 
			y=rand()%10;
		}
		else
		{
			x=rand()%20;//隨機數(shù) 
			y=rand()%20;
		}
		if(f==1)
		{
			sum=x+y;
			cout << x << " + " << y << " = " << endl;
		}
		else if(f==2)
		{
			sum=x-y;
			cout << x << " - " << y << " = " << endl;
		}
		else if(f==3)
		{
			sum=x*y;
			cout << x << " * " << y << " = " << endl;
		}
		else if(f==4)
		{
			sum=x/y;
			cout << x << " / " << y << " = " << endl;
		}
			cout << "Please enter the answer :" << endl;
			cin >> a;
			if(a==sum)
			{
				right++; 
				switch(rand()%4)
				{
					case 0:	cout << "Very good!            " << endl << endl;break;
					case 1:	cout << "Excellent!            " << endl << endl;break;
					case 2:	cout << "Nice work!            " << endl << endl;break;
					case 3:	cout << "Keep up the good work!" << endl << endl;break;
				}
			}
			else
			{
				switch(rand()%4)
				{	
					case 0:	cout << "No. Please try again." << endl << endl;break;
					case 1:	cout << "Wrong. Try once more." << endl << endl;break;
					case 2:	cout << "Don't give up!       " << endl << endl;break;
					case 3:	cout << "No. Keep trying.     " << endl << endl;break;
				}
			}
	}while(count<10);
	s=right*1.0/count;//計算正確率 
	if(s<0.75)
	{
		cout <<"Please ask your instructor foe extra help !!!" << endl;
	}
	return 0;
}