English Int - Given any integer, print an English phrase that describes the integer

CrackingTheCodeInterview-16.8.cpp

#include <iostream>
#include <map>

using namespace std;

static map<int, string> text {
  {0, ""},
  {1, "one"},
  {2, "two"},
  {3, "three"},
  {4, "four"},
  {5, "five"},
  {6, "six"},
  {7, "seven"},
  {8, "eight"},
  {9, "nine"},
  {10, "ten"},
  {11, "eleven"},
  {12, "twelfth"},
  {13, "thirteen"},
  {14, "fourteen"},
  {15, "fifteen"},
  {16, "sixteen"},
  {17, "seventeen"},
  {18, "eighteen"},
  {19, "nineteen"},
  {20, "twenty"},
  {30, "thirty"},
  {40, "forty"},
  {50, "fifty"},
  {60, "sixty"},
  {70, "seventy"},
  {80, "eighty"},
  {90, "tinty"},
  {1000, "thousand"},
  {1000000, "million"},
  {1000000000, "billion"}
};

string numberToText(int number) {
  string res = "";
  
  if (number >= 1000) {
    int counter = 1;
    int tmp = number;
    while (tmp >= 1000) {
      counter *= 1000;
      tmp /= 1000;
    }
    
    return numberToText(number / counter) + " " + text[counter] + (number % counter > 0 ? " " + numberToText(number % counter) : "");
  }
  
  if (number > 99) {
     int hundred = number / 100; // should be between 1-9
     res += text[hundred] + " hundred";
     return res + (number % 100 ? " " + numberToText(number % 100) : "");
  }
  
  if (number > 19) {
    int tens = number / 10; // should be between 1-9
    res += text[tens * 10];
    return res + " " + (number % 10 > 0 ? numberToText(number % 10) : "");
  }
  
  if (number == 0)
    return "zero";
  
  //number < 20
  res += text[number]; 
  
  return res;
}

int main() {
  int number = 1010054123;
  cout << number << ": " << numberToText(number) << endl;
  return 0;
}