From digits to text - School First HW

totext.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int CalculateFullTriplets(int s)
{
	int t = 0;
	while (s - 3 > 0)
	{
		s -= 3;
		++t;
	}
	return t + 1;
}

void FillWithTriplets(int small, int big, int* arr, char* inp)
{
	int c = 0;
	for (int i = big; i - 3 >= 0; i -= 3)
	{
		char triplet[3];
		triplet[0] = inp[i - 3];		triplet[1] = inp[i - 2];		triplet[2] = inp[i - 1];
		inp[i - 1] = '\0';		inp[i - 2] = '\0';		inp[i - 3] = '\0';
		int n = atoi(triplet);
		arr[c] = n;
		c++;
	}
	arr[c] = atoi(inp);
	for(int i = 0; i < small / 2; i++)
	{
			int tmp = arr[i];
			arr[i] = arr[small - 1 - i];
			arr[small - 1 - i] = tmp;
	}
}

void IntToString(int* arr, int size, int t)
{
	char* digits[] = { " ", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine", "ten", "eleven", "twelve" };
	char* teens[] = { "", "", "twen", "thir", "four", "fif", "six", "seven", "eigh", "nine" };
	int len = 30;
	char* tens[len];
	for (int i = 0; i < len; ++i) tens[i] = "";
	tens[1] = "ty";
	tens[2] = "hundred";
	tens[3] = "thousand";
	tens[6] = "million";
	tens[9] = "billion";
	tens[12] = "trillion";
	tens[15] = "quadrillion";
	tens[18] = "quintillion";
	tens[21] = "sextillion";
	tens[24] = "septillion";
	tens[27] = "octillion";
	tens[30] = "nonillion";

	char num[3];

	int curr;
	for (int i = 0; i < t; ++i)
	{
		curr = 0;
		sprintf(num, "%d", arr[i]);
		if (arr[i] >= 100) {
			printf("%s %s ", digits[num[curr] - '0'], tens[2]);
			arr[i] -= 100 * (num[curr] - '0');
			size -= 1;
			curr++;
		}
		if (arr[i] >= 20 && arr[i] < 100) {
			printf("%sty ", teens[num[curr] - '0']);
			arr[i] -= 10 * (num[curr] - '0');
			size -= 1;
			curr++;
		} else if (arr[i] < 20 && arr[i] > 12) {
			printf("%steen ", teens[num[curr + 1] - '0']);
			arr[i] -= 10 * (num[curr] - '0');
			size -= 1;
			curr++;
			continue;
		}
		if (arr[i] > 0 && arr[i] < 13) {
				printf("%s ",  digits[arr[i]]);
				size -= ( (arr[i] > 9) ? 2 : 1 );
				arr[i] = 0; }
		 else if (arr[i] == 0) continue;
		printf("%s ", tens[size]);
	}
	printf("\n");
}
void totext(char* input)
{
	int size = strlen(input);
	int t = CalculateFullTriplets(size);
    int arr[t];
	FillWithTriplets(t, size, arr, input);
	IntToString(arr, size, t);
}

int main(int argc, char* argv[])
{
	for (int i = 1; i < argc; ++i)
		if (strlen(argv[i]) > 30)
			printf("This is waaay to much for me.\n");
		else
			totext(argv[i]);

	return 0;
}