Optimize multiple if else statements in C

Question

Code:

#include <stdio.h>
    int main(void)
    {
        int coins = 0;
        float cash_owed = 0;
        printf("Cash owed: ");
        scanf("%f" , &cash_owed);
        while(cash_owed > 0)
        {
            if(cash_owed >= 0.25)
            {
                cash_owed -= 0.25;
                coins++;
            }
            else if(cash_owed >= 0.10)
            {
                cash_owed -= 0.10;
                coins++;
            }
            else if(cash_owed >= 0.05)
            {
                cash_owed -= 0.05;
                coins++;
            }
            else if(cash_owed >= 0.01) 
            {
                cash_owed -= 0.01;
                coins++;
            }
        }
        printf("%i\n", coins);
        return 0;
    }

So basically this is a greedy algorithm. It takes cash owed as inputs, Evaluates the minimum no. of coins to give. (US Currency). I think there is so much repeatation in my code. It's not optimized. Can someone help me out here?

Answer 1

Firstly, you should never (unless you come of with a good reason, and "there are 100 cents in one dollar" is not a good reason) use floating point numbers for currency. They can generate rounding error bugs. Use integers instead, and format output later.

And using that, I would do something like this:

int coins = 0;
int cash_owed = 0;
printf("Cash owed (in cents): ");
scanf("%d" , &cash_owed);

int coin_type[] = {25, 10, 5, 1};

for(int i=0; i<sizeof(coin_type)/sizeof(coin_type[0]); i++) {
    while(cash_owed >= coin_type[i]) {
        cash_owed -= coin_type[i];
        coins++;
    }
}

Here is an example of how to print currency:

int cents = 7334;
printf("$%d.%d", cents/100, cents%100);