What is wrong with this code for greedy (pset1)?

Question

I have written the following code as a part of pset1 for greedy. I always seem to get a number less than the actual number of coins.Please help me out.

#include <stdio.h>
#include <cs50.h>

int main(void)
{
    int n=0, x;
    float c;
    do
    {
        printf("O hai! How much change is owed?\n");
        c=GetFloat();

        if((c/0.25)>=1)
        {
            x=c/0.25;
            n=n+x;
            c=c-(x*0.25);
        }
        if((c/0.10)>=1)
        {
            x=c/0.10;
            n=n+x;
            c=c-(x*0.10);
        }
        if((c/0.05)>=1)
        {
            x=c/0.05;
            n=n+x;
            c=c-(x*0.05);
        }

        n=n+(c*100);

    }while(c<=0);
    printf("%i\n", n);
}

Answer 1

You are not learning what this pset is trying to teach you. That the floats in your computer are stored imprecisely. Take a look at the following program:

float_test.c

#include "stdio.h"
#include "cs50.h"

int main(void)
{
    float number;
    number = GetFloat();

    printf("%.25f\n", number);
}

And now take a look at its output, for input 0.51. (any number would be the same)

night@hawk:~$ ./float_test
0.51
0.5099999904632568359375000
1

See that the 0.51 I gave, is not stored as 0.51, but as 0.5099999904632568359375000 if I print the first 25 decimal digits. That's the reason you are supposed to use integers instead of floats.

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