Update readme, create factorial_examples folder and move existing code into it

factorial_examples/factorial.c

@@ -0,0 +1,37 @@
+#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) {
+		puts("Error reading line from user input");
+		return 1;
+	}
+
+	uintmax_t user_input = abs(atoi(*lineptr));
+	printf("\nRecursive factorial for number: %ju\n", factorial(user_input));
+	printf("Iterative factorial for number: %ju\n", factorial_iter(user_input));
+	free(lineptr);
+	return 0;
+}