/*
 * CHANGE -- figure out how many quarters, dimes, nickels, pennies 
 * are in some amount of cash
 *
 * Usage: change
 *
 * Inputs: User enters an integer for change
 * Outputs: number of quarters, dimes, nickels, pennies in the change
 * Exit Code: EXIT_SUCCESS (0) if valid integer entered
 *            EXIT_FAILURE (1) otherwise
 * WARNING: Input must begin with an integer, but is not checked beyond that
 *
 * written for ECS 036A, Fall 2019
 *
 * Matt Bishop, UC Davis
 * * 09/20/2019: original program written
 * * 10/03/2019: add loop to handle non-numeric inputs
 * * 10/04/2019: add check for negative number inputs
 */
#include <stdio.h>
#include <stdlib.h>

int main(void)
{
	int ch;				/* used to clear bogus line */
	int amount;			/* how much change the user has */
	int leftover;		/* used to hold amount as it decreases */
	int numquarters;	/* how many quarters */
	int numdimes;		/* how many dimes */
	int numnickels;		/* how many nickels */
	int numpennies;		/* how many pennies */

	/* prompt the user for input */
	printf("Amount of change to convert to coins: ");

    /* read in an amount; loop until you get it */
    while ((ch = scanf("%d", &amount)) != 1 || amount < 0){
		/* exit at EOF */
		if (ch == EOF)
        	return(EXIT_FAILURE);
		/* oops ... bad input */
	    printf("Amount must be nonnegative integer\n");
		/* now clear the rest of the line */
		while ((ch = getchar()) != EOF && ch != '\n')
			/* do nothing */ ;
		/* otherwise reprompt */
		printf("Amount of change to convert to coins: ");
	}
	leftover = amount;

    /* computer the number of quarters and how much is left over */
    numquarters = leftover / 25;
    leftover = leftover % 25;

    /* computer the number of dimes and how much is left over */
    numdimes = leftover / 10;
    leftover = leftover % 10;

    /* computer the number of nickels and how much is left over */
	numnickels = leftover / 5;
    leftover = leftover % 5;

    /* whatever is left over is the number of pennies */
    numpennies = leftover;

    /* print the result */
     printf("%d cents is %d quarters, %d dimes, %d nickels, and %d pennies\n",
                            amount, numquarters, numdimes, numnickels, numpennies);

	/* thank you and goodnight! */
	return(EXIT_SUCCESS);
}