/* File: subtractionTutorLoop.cpp

   Modified example from ch. 4.

   Uses nested while loops:

   The outer loop is an eof-controlled while loop that
   prompts the user for the number of questions to ask.

   The inner loop conducts a single quiz.
*/

#include <iostream>
#include <ctime> 				// for time()
#include <cmath> 				// for the srand(), rand()
using namespace std;

int main(){

	int correctCount,			// number of correct answers
	   count = 0,				// Count the number of questions
	   noOfQues,				// number of questions on quiz
	   answer; 				// user's answer for a quiz question
	long startTime, endTime,		// quiz timer variables
	   elapsedTime;

	//prompt and read number of quiz questions
	cout << "enter number of questions for quiz (c-z to exit): ";
	cin >> noOfQues;

	//driver loop
	while(cin){

		//initialze quiz counters
		count = 0;
		correctCount = 0;
		long startTime = time(0);
		cout << endl;

		//execute one quiz & display stats
		while (count < noOfQues){
			// 1. Generate two random single-digit integers
			srand(time(0));
			int number1 = rand() % 10;
			int number2 = rand() % 10;

			// 2. If number1 < number2, swap number1 with number2
			if (number1 < number2){
				int temp = number1;
				number1 = number2;
				number2 = temp;
			}

			// 3. Prompt the student to answer “what is number1 – number2?”
			cout << "What is " << number1 << " - " << number2 << "? ";
			cin >> answer;

			// 4. Grade the answer and display the result
			if (number1 - number2 == answer) {
				cout << "You are correct!\n";
				correctCount++;
			}
			else
				cout << "Your answer is wrong.\n" << number1 << " - " <<
				number2 << " should be " << (number1 - number2) << endl;

			// Increase the count
			count++;
		}

		//display quiz stats
		endTime = time(0);
		elapsedTime = endTime - startTime;
		cout << "Correct count is " << correctCount << "\nTest time is "
			 << elapsedTime << " seconds\n" << endl;

		//prompt and read number of quiz questions
		cout << "enter number of questions for quiz (c-z to exit): ";
		cin >> noOfQues;
	}

	//exit program
	return 0;
}