Greedy calculator in C - c

Question

I need to create a greedy calculator that accepts only .25, .10, .5 and .1.
I need to print the minimum amount of coins needed to fulfil the change.
This is going on a loop and I can't see what to do to fix it.
I am still learning, go easy on me :)
#include <stdio.h>
#include <cs50.h>
#include <math.h>
int main(void) {
int coins = 0;
int change;
int i;
do {
change = get_float("How much change? ");
}
while (change <= 0); /* condition for acceptance*/
int cents = round(change * 100);
if (cents > 0) { /* run all whiles we get to 1c*/
while ((cents - 25) >= 25) { /* run 25c */
coins += 1;
}
while ((cents - 10) >= 10) { /* run 10c*/
coins += 1;
}
while ((cents - 5) >= 5) { /* run 5c*/
coins += 1;
}
while ((cents - 1) >= 1) { /* run 1c*/
coins += 1;
}
} else {
printf("%d", coins);
}
}

Answer 1

There are multiple problems in your code:
change is defined as an int, so the amount entered by the user is truncated before the computation even starts, producing an incorrect result.
you do not update cents in any of the loops, so you get an infinite loop if any of these conditions is true.
note that the conditions are incorrect: (cents - 25) >= 25 is true if cents is greater or equal to 50.
the test if (cents > 0) is incorrect. You would only print the number of coins if cents <= 0.
the last loop is useless, the number of remaining cents is the number of pennies to count.
Here is a modified version:
#include <stdio.h>
#include <cs50.h>
#include <math.h>
int main(void) {
float change;
do {
change = get_float("How much change? ");
}
while (change <= 0); /* condition for acceptance*/
int cents = round(change * 100); /* avoid rounding issues */
int coins = 0;
while (cents >= 25) { /* count quarters */
cents -= 25;
coins += 1;
}
while (cents >= 10) { /* count dimes */
cents -= 10;
coins += 1;
}
while (cents >= 5) { /* count nickels */
cents -= 5;
coins += 1;
}
count += cents; /* count pennies */
printf("%d\n", coins);
return 0;
}

Answer 2

The cents variable never changes. (cents - 25) indeed returns the value of current cents minus 25, but you don't assign it to cents variable, so one of those 4 while loops will always be true.
There is also another probem: get_float function returns float while change variable is int, if the user were to enter a value less than 1, such as .5, it would be casted to 0 and prompt again and again until the user enters a value greater than 1. Also note you would probably get a wrong answer for any non-integer input.