A program to represent a coin amount using the smallest number of coins

Recently, I was learning about greedy algorithms. One example that was given was an algorithm for exchanging a given money amount using the smallest number of coins. After the lecture, I wrote a C program implementing this:

#include 
#include 
#include 

static int compareDenominations(const void *a, const void *b) {
    return (*((int*) b) - *((int*) a));
}

int main(int argc, char *argv[]) {
    long amount;
    int count;
    long *denominations;
    if (argc > 2) {
        errno = 0;
        amount = strtol(argv[1], NULL, 10);
        if (errno || amount = denominations[i]) {
            amount -= denominations[i];
            denominationCount++;
        }
        denominations[i] = denominationCount;
    }
    if (amount) {
        puts("The coin amount could not be represented using the given denominations.");
        return EXIT_FAILURE;
    }
    printf("Counts: [ ");
    for (i = 0; i < count; i++) {
        printf("%ld ", denominations[i]);
    }
    puts("]");
    return EXIT_SUCCESS;
}

Because my program can accept arbitrary inputs, this greedy algorithm may not always output the most optimal solution, but I am still interested in the quality of my implementation.

-
Don't invent error messages. If strtol sets errno, use perror() to print a precise reason for a failure.

-
Flat is better than nested. I recommend to handle argc

-
Testing for duplicated denomination is easier after they are sorted.

-
while (amount >= denominations[i]) loop is a long way to say

denominationCount = amount / denomination[i];
amount %= denomination[i];

-
You may want to break the for (i = 0; i

-
Qudos for sizeof(*denominations).

-
The algorithm may fail to find a solution.

StackExchange Code Review Q#145238, answer score: 8