#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>
#include <stdint.h>

uintmax_t factorial(uintmax_t n) {
	if(n < 2)
		return 1;
	return n * factorial(n-1);
}

uintmax_t factorial_iter(uintmax_t n) {
	uintmax_t fact = 1;
	uintmax_t i = 2;
	while(i <= n) {
		fact *= i;
		i++;
	}
	return fact;
}

int main(void) {
	size_t bufsize = 1024;
	char *lineptr = calloc(bufsize, sizeof(char));
	fputs("Enter number to factor: ", stdout);
	int err = getline(&lineptr, &bufsize, stdin);
	if(err == -1) {
		fputs("Error reading line from user input\n", stderr);
		free(lineptr);
		return 1;
	}

	uintmax_t user_input = abs(atoi(lineptr));
	free(lineptr);
	printf("\nRecursive factorial for number: %ju\n", factorial(user_input));
	printf("Iterative factorial for number: %ju\n", factorial_iter(user_input));
	return 0;
}