CS50 pset1 Greedy not working - c

Question

Like others here, I am trying to make a program called greedy that will tell me the least amount of coins that I have to give someone as change for a given amount of money. I made this but it gives me the wrong amount of coins and I don't know why :(
#include <stdio.h>
#include <cs50.h>
#include <math.h>
int main(void)
{
float given_amount;
int cent_count;
int coin_count = 0;
do
{
printf("What is the amount of change I owe you?\n");
given_amount = GetFloat();
}
while (given_amount < 0);
cent_count = (int)round(given_amount * 100);
while (cent_count > 25)
{
coin_count++;
cent_count -= 25;
}
while (cent_count > 10)
{
coin_count++;
cent_count -= 10;
}
while (cent_count >= 1)
{
coin_count++;
cent_count -= 1;
}
printf("Take these %d coins\n", coin_count);
}
If I tell the program I need to give back 25 cents the program tells me I have to give the person 7 coins, but it should just tell me I have to give him one coin... a quarter.

Answer 1

Your first 2 loops don't take care of value 25 and 10.
In fact your algorithm is giving you 7, that is: 2 coins of 10 cent, and 5 coins of 1 cent.
You must check for them, so:
while (cent_count >= 25)
{
coin_count++;
cent_count -= 25;
}
while (cent_count >= 10)
{
coin_count++;
cent_count -= 10;
}

Answer 2

Here's my code:
#include <cs50.h>
#include <stdio.h>
#include <math.h>
int main(void)
{
float input = -1.00;
int n = 0;
int c = 0;
printf("O hai! How much change is owed?: ");
do
{
input = GetFloat();
if(input < 0)
printf("Positive number, please!: ");
}
while (input < 0);
c = roundf(input * 100);
while(c >= 25)
{
c = c - 25;
n++;
}
while (c >= 10)
{
c = c - 10;
n++;
}
while (c >= 5)
{
c = c - 5;
n++;
}
n = n + c;
printf("%i\n", n);
}