/*
Programmer: Greg Perkins
Program:	TTTutor.c
Written:	May 27, 1998

This program was designed with the young student in mind.  It is a Times Table Tutor.
It generates random times tables and gives the student two chances to get the right
answer.  If the student is unable to get the right answer, he/she is shown a 
'walk-through' on the way to get the right answer.  It continually gives the student
words of encouragement to keep them working.
*/

#include <stdio.h>

void clear (void);

main()
{
	int num1, num2, answer, i, j;
	int sum, last_sum, num_correct;
	int again = 1, num_tries, num_problems;
	float score;
	char dummy, cont;
	
	srand( clock() );	/* seed the random number generator */
	
	printf("Welcome to the Times Table Tutor!\n\n");
	
	printf("I will help you learn your times tables.\n\n");
	
	printf("I will give you ten times tables and keep score for you.\n");
	printf("You will get two tries to answer the question correctly.  If\n");
	printf("you don't get the right answer after the first try, I will\n");
	printf("give you a hint and then let you try again.  If you don't get\n");
	printf("the right answer the second time, I will show you how to solve\n");
	printf("the problem by taking you through it step by step.\n\n");
	printf("Now, let's have some fun...\n");
	printf("Hit ENTER to continue...\n");
	
	dummy = getchar();

	while (again)
	{
		num_correct = 0;
		
		clear();
		
		for (num_problems = 1; num_problems <= 10; num_problems++)
		{	
			clear();
		
			num1 = (rand() % 13);	/* get a random number between 0 and 12 */
			num2 = (rand() % 13);	/* get a random number between 0 and 12 */
		
			printf("\nProblem #%2d :    %2d\n", num_problems, num1);
			printf("              X  %2d\n", num2);
			printf("             ------\n");
			printf("Enter Answer    ");
			if ((num1*num2) < 10)
				printf("  ");		/* align the answer correctly */
			else if ((num1*num2) < 100)
				printf(" ");
			else
				printf("");		
			scanf("%d", &answer);
			dummy = getchar();
			
			if (answer == (num1*num2))
			{
				printf("\nYou are correct.  Great job!!!  I knew you could do it.\n");
				num_correct++;
			}
			else	
			{
				clear();
				
				printf("Ooops!!!  Better try that one again...\n");
				if ((num1 == 0) || (num2 == 0))
				{
					printf("\n***** SPECIAL CASE *****");
					printf("\n\nHINT:  0 times ANY number ALWAYS equals zero.\n");
				}
				else
				{	
					printf("\n\nHINT:  To find the correct answer, start with zero and add %d (%d times).\n", num1, num2);
					printf("Example: 0 + ");
					for (i = 1; i <= num2; i++)
					{
						printf("%d", num1);
						if (i == num2)
							printf(" = ???\n");
						else
							printf(" + ");
					}
				}
						
				printf("\nLet's try that one again...\n");
				printf("Problem #%2d :    %2d\n", num_problems, num1);
				printf("              X  %2d\n", num2);
				printf("             ------\n");
				printf("Enter Answer    ");
				if ((num1*num2) < 10)
					printf("  ");		/* align the answer correctly */
				else if ((num1*num2) < 100)
					printf(" ");
				else
					printf("");		
				scanf("%d", &answer);
				dummy = getchar();
				
				if (answer == (num1*num2))
				{
					printf("\nCorrect.  Good job!!!  Remember the hint, okay?\n");
					num_correct++;
				}	
				else		/* two incorrect answers invokes the talk through */
				{
					sum = last_sum = 0;
					
					clear();
					
					printf("\nIt looks like you are having a little trouble...\n");
					printf("We'll do this one together...Okay?\n");
					printf("\nThe correct answer is : %d X %d = %d\n", num1, num2, num1*num2);
					printf("\nHere is how to find the answer:\n");
					printf("We are going to start with zero and add %d (%d times).\n", num1, num2);
					printf("Hit ENTER after each step to continue...\n\n");
					if (num2 == 0)
					{
						printf("Step %2d : %3d  + %3d = %3d", 1, last_sum, last_sum, last_sum);
						dummy = getchar();
					}	
					for (j = 1; j <= num2; j++)
					{
						sum += num1;
						printf("Step %2d : %3d  + %3d = %3d", j, last_sum, num1, sum);
						dummy = getchar();
						last_sum = sum;
					} /* for loop */	
					printf("The correct answer is : %d\n\n", sum);
					
					printf("\nDon't worry!!!  I know you'll get it the next time!!!\n");
					printf("Hit ENTER to continue...");
					dummy = getchar();
				}
			} /* first answer incorrect else clause */
		} /* num_tries loop */	
			
			/* display the final score */
			clear();
			score = (((float)num_correct/(float)(num_problems-1))*100);	
			printf("\nNumber of Problems : %3d\n", num_problems-1);
			printf("Number Correct     : %3d\n", num_correct);
			printf("Score (percentage) : % 3.1f%%\n\n\n", score);	
			
			/* display final words of encouragement */
			if (score == 100)
				printf("Outstanding!!!  You are a times table genius!!!  Keep up the hard work.\n");
			else if (score < 60)
				printf("We need to practice some more.  I say we do it again.\n");
			else if (score < 70)
				printf("Pretty good, but we still need practice.  Let's do it again...Okay?\n");
			else if (score < 80)
				printf("Good job!!!  Let's try to get 80%% next time...Okay?\n");
			else if (score < 90)
				printf("Great job!!!  With a little more practice, I know we can get 90%%!\n");
			else
				printf("Terrific!!!  You sure are good at your times tables!!!\n");
								
			/* prompt the user to do it again */
			printf("\nWould you like to do another set? (y/n)\n");
			scanf("%c", &cont);
			dummy = getchar();	/* clean up the I/O stream */
		
			if ((cont == 'y') || (cont == 'Y'))
				again = 1;
			else
				again = 0;			
	} /* main while loop */
}	

void clear (void)
{
	int k;
	
	for (k = 1; k < 20; k++)
		printf("\n\n\n");
}