17.c

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

char digits[20][10] = {
  "",
  "One",
  "Two",
  "Three",
  "Four",
  "Five",
  "Six",
  "Seven",
  "Eight",
  "Nine",
  "Ten",
  "Eleven",
  "Twelve",
  "Thirteen",
  "Fourteen",
  "Fifteen",
  "Sixteen",
  "Seventeen",
  "Eighteen",
  "Nineteen"
};
char tens[11][10] = {
  "",
  "",
  "Twenty",
  "Thirty",
  "Forty",
  "Fifty",
  "Sixty",
  "Seventy",
  "Eighty",
  "Ninety"
};

void word(int num) {
  if (num / 100)
    printf("%s Hundred ", digits[num / 100]);
  if ((num % 100) < 20 && (num % 100) > 0)
    printf("%s ", digits[num % 100]);
  else if ((num / 10) % 10) {
    printf("%s ", tens[(num / 10) % 10]);
    if (num % 10)
      printf("%s ", digits[num % 10]);
  }
}

int main() {
  int t;
  scanf("%d", & t);
  while (t--) {
    long long int num;
    scanf("%lld", & num);
    int tn = num / 1000000000000;
    int bn = (num / 1000000000) % 1000;
    int mn = (num / 1000000) % 1000;
    int th = (num / 1000) % 1000;
    int hd = num % 1000;
    //printf("%d %d %d %d %d\n", tn, bn, mn, th, hd);
    if ((tn + bn + mn + th + hd) == 0)
      printf("Zero");
    if (tn) {
      word(tn);
      printf("Trillion ");
    }
    if (bn) {
      word(bn);
      printf("Billion ");
    }
    if (mn) {
      word(mn);
      printf("Million ");
    }
    if (th) {
      word(th);
      printf("Thousand ");
    }
    if (hd) {
      word(hd);
    }
    printf("\n");
  }
  return 0;
}