/* 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>
#include <iostream>

using namespace std;

/* 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 */
    string 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 */
    string 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*/
    string tens_multiple[] = {"", "", "twenty", "thirty", "forty", "fifty",
                             "sixty", "seventy", "eighty", "ninety"};

    string tens_power[] = {"hundred", "thousand"};

    /* Used for debugging purpose only */
    printf("\n%s: ", num);

    /* For single digit number */
    if (len == 1) {
        cout << 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) {
                cout << single_digits[*num - '0'] << " ";
                cout << 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';
                cout << two_digits[sum] << " ";
                return;
            }

            /* Need to explicitely handle 20 */
            else if (*num == '2' && *(num + 1) == '0') {
                cout << "twenty ";
                return;
            }

            /* Rest of the two digit numbers i.e., 21 to 99 */
            else {
                int i = *num - '0';
                cout << (i? tens_multiple[i]: "") << " ";
                ++num;
                if (*num != '0')
                    cout << single_digits[*num - '0'] << " ";
            }
        }
        ++num;
    }
}

/* Driver program to test above function */
int main(void)
{
    cout << "Enter a number to convert to words:- ";

    char num[10];

    cin >> num;
    convert_to_words(num);

    cout << endl;

    return 0;
}