Question

• develop an algorithm and then a C program that accomplishes the following.
  • determines the minimum number of quarters, dimes, nickels, and pennies to make change for any amount of cents from 1 cent to 99 cents inclusive;
  • produces an error message if 0 or more than 99 is entered as input, but the program will keep running and ask for another input;
  • terminate if 0 or a negative number is entered.
  • Here is possible example of the program running (remember that there could be any number of inputs (perhaps 1,000,000) but all inputs are integers)

Hints: use if / else if / else... use % and /... use a while loop or a do while loop

example:

Please enter the number of cents, from 1 through 99, or enter a negative number to quit:  31
             Quarters: 1   Dimes: 0   Nickels: 1   Pennies: 1
               Please enter the number of cents, from 1 through 99, or enter a negative number to quit:  89
               Quarters: 3 Dimes: 1 Nickels: 0 Pennies: 4
               Please enter the number of cents, from 1 through 99, or enter a negative number to quit:  121
   Your entered a value outside the range.
               Please enter the number of cents, from 1 through 99, or enter a negative number to quit:  0
   Your entered a value outside the range.
               Please enter the number of cents, from 1 through 99, or enter a negative number to quit:  18
               Quarters: 0 Dimes: 1 Nickels: 1 Pennies: 3
   Your entered a value outside the range.
               Please enter the number of cents, from 1 through 99, or enter a negative number to quit:  -666   
               Thanks for using my program. Good bye.

Answer 1

Steps to follow:

1. Define an array for value of Quarter as 25, Dimes as 10, Nickels as 5 and Pennies as 1.
2. Define an array of size 4 to store count of each coin type used
3. Run a for loop and get minimum coin number of each coin type by dividing the cents value (from the user) with the coin value, and also updating the cents value (from user) by taking the modulus with the coin value.
4. Check for negative value input from user to exit the program and the values that are not in range.

Code:

#include <stdio.h>

void minCoins(int value)
{       
        // coin value array representing indices 0 - quarters, 1 - dimes,  2 - nickels, 3 - pennies.
        int coin_value[4] = {25, 10, 5, 1};
        
        // result array to store number of coins for each coin type in same order
        int coin_num[4] = {0, 0, 0, 0};
                
                // using for loop and divide & modulus operator to get number of coins & remaining value respectively 
                // for every coin type
                
                for (int i = 0; i < 4; i++) { 
                    coin_num[i] = value / coin_value[i];
                    value = value % coin_value[i];
                } 
                
        // Output of total no. of coins with each coin type number
                printf("Quarters: %d ", coin_num[0]);
                printf("Dimes: %d ", coin_num[1]);
                printf("Nickels: %d ", coin_num[2]);
                printf("Pennies: %d \n", coin_num[3]);
                
}

int main() {
    int num;
    while (1) {
        printf("Please enter the number of cents, from 1 through 99, or enter a negative number to quit: ");
        scanf("%d", &num);
        if (num < 0) {
            printf("Thanks for using my program. Good bye.");
            break;
        }
        else {
            if (num > 0 && num < 100)
                minCoins(num);
            else
                printf("Your entered a value outside the range.\n");
        }
    }
    return 0;
}

Output: