zoho -Program to convert a given number to words

Program to convert a given number to words

Write code to convert a given number into words. For example, if “1234” is given as input, output should be “one thousand two hundred thirty four”.

The code supports numbers up-to 4 digits, i.e., numbers from 0 to 9999. Idea is to create arrays that store individual parts of output strings. One array is used for single digits, one for numbers from 10 to 19, one for 20, 30, 40, 50, .. etc, and one for powers of 10.
The given number is divided in two parts: first two digits and last two digits, and the two parts are printed separately.

CODING:

/* Program to print a given number in words. The program handles
numbers from 0 to 9999 */
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
/* A function that prints given number in words */
void convert_to_words(char *num)
{
 int len = strlen(num); // Get number of digits in given number
 /* Base cases */
 if (len == 0) {
  fprintf(stderr, "empty string\n");
  return;
 }
 if (len > 4) {
  fprintf(stderr, "Length more than 4 is not supported\n");
  return;
 }
 /* The first string is not used, it is to make array indexing simple */
 char *single_digits[] = { "zero", "one", "two", "three", "four",
       "five", "six", "seven", "eight", "nine"};
 /* The first string is not used, it is to make array indexing simple */
 char *two_digits[] = {"", "ten", "eleven", "twelve", "thirteen", "fourteen",
     "fifteen", "sixteen", "seventeen", "eighteen", "nineteen"};
 /* The first two string are not used, they are to make array indexing simple*/
 char *tens_multiple[] = {"", "", "twenty", "thirty", "forty", "fifty",
       "sixty", "seventy", "eighty", "ninety"};
 char *tens_power[] = {"hundred", "thousand"};
 /* Used for debugging purpose only */
 printf("\n%s: ", num);
 /* For single digit number */
 if (len == 1) {
  printf("%s\n", single_digits[*num - '0']);
  return;
 }
 /* Iterate while num is not '\0' */
 while (*num != '\0') {
  /* Code path for first 2 digits */
  if (len >= 3) {
   if (*num -'0' != 0) {
    printf("%s ", single_digits[*num - '0']);
    printf("%s ", tens_power[len-3]); // here len can be 3 or 4
   }
   --len;
  }
  /* Code path for last 2 digits */
  else {
   /* Need to explicitly handle 10-19. Sum of the two digits is
   used as index of "two_digits" array of strings */
   if (*num == '1') {
    int sum = *num - '0' + *(num + 1)- '0';
    printf("%s\n", two_digits[sum]);
    return;
   }
   /* Need to explicitely handle 20 */
   else if (*num == '2' && *(num + 1) == '0') {
    printf("twenty\n");
    return;
   }
   /* Rest of the two digit numbers i.e., 21 to 99 */
   else {
    int i = *num - '0';
    printf("%s ", i? tens_multiple[i]: "");
    ++num;
    if (*num != '0')
     printf("%s ", single_digits[*num - '0']);
   }
  }
  ++num;
 }
}
/* Driver program to test above function */
int main(void)
{
 convert_to_words("9923");
 convert_to_words("523");
 convert_to_words("89");
 convert_to_words("8989");
 return 0;
}

OUTPUT:

9923: nine thousand nine hundred twenty three
523: five hundred twenty three
89: eighty nine
8989: eight thousand nine hundred eighty nine