Convertir Números a Letras en C++

Hola amig@s esta vez les traigo un conversor de números enteros a su equivalente en letras.

Captura:

Código:

Números a letras.cpp:

#include <iostream>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <windows.h> 
#include <time.h>
#define N 11 //define la longitud maxima que es posible para el numero
using namespace std;
//PROTOTIPOS
void unidades(char num[N],int x);
void unidades2(char num[N],int x);
bool decenas(char num[N],int x);
void centenas(char num[N],int x);
void miles(char num[N],int x);
bool dec_miles(char num[N],int x);
void cent_dmiles(char num[N],int x);
void millones(char num[N],int x);
bool decenas_mill(char num[N],int x);
void cent_mill(char num[N],int x);
void gotoxy(int x, int y);
int main(){
 char num[N];
 bool b,a;
 int x,y=-1,i;
 system("color 1f");
 do{
  system("title Conversor de Numeros a letras");
  system("cls");
  fflush(stdin);
  do{a=true;
  b=true;
  cout<<"\nIngrese el numero: ";cin.getline(num,N);
  x=strlen(num);}while(x<1||x>10); fflush(stdin);cout<<"\n\n";
  while(x>=1){
   y++;
   fflush(stdin);
   switch(x){
   case 1:if(a==true&&b==true)unidades(num,y);a++;if(num[0]=='0'){x=1;}break;
   case 2:b=decenas(num,y);if(num[y+1]=='0'){x=1;}break;
   case 3:centenas(num,y);break;
   case 4:if(b==true)miles(num,y);break;
   case 5:b=dec_miles(num,y);break;
   case 6:cent_dmiles(num,y);break;
   case 7:millones(num,y);break;
   case 8:b=decenas_mill(num,y);break;
   case 9:cent_mill(num,y);break;
   case 10: cout<<"Lo siento pero puedo convertir hasta 999,999,999";x=1;break;
   }//cout<<"["<<x<<"]";
   --x;
   fflush(stdin);
  }y=-1;
  fflush(stdin);
  cout<<"\n\n\nSalir 0: ";cin>>i;}while(i!=0);
}

void unidades(char num[N],int x){
 switch(num[x]){//UNIDADES
 case '0':cout<<"cero"<<" ";break;
 case '1':cout<<"uno"<<" ";break;
 case '2':cout<<"dos"<<" ";break;
 case '3':cout<<"tres"<<" ";break;
 case '4':cout<<"cuatro"<<" ";break;
 case '5':cout<<"cinco"<<" ";break;
 case '6':cout<<"seis"<<" ";break;
 case '7':cout<<"siete"<<" ";break;
 case '8':cout<<"ocho"<<" ";break;
 case '9':cout<<"nueve"<<" ";break;
 }
}
void unidades2(char num[N],int x){
 switch(num[x]){//UNIDADES
 case '1':cout<<"once"<<" ";break;
 case '2':cout<<"doce"<<" ";break;
 case '3':cout<<"trece"<<" ";break;
 case '4':cout<<"catorce"<<" ";break;
 case '5':cout<<"quince"<<" ";break;
 case '6':cout<<"dieciseis"<<" ";break;
 case '7':cout<<"diecisiete"<<" ";break;
 case '8':cout<<"dieciocho"<<" ";break;
 case '9':cout<<"diecinueve"<<" ";break;
 }
}
bool decenas(char num[N],int x){
 bool r=true;
 switch(num[x]){//DECENAS
 case '1':if(num[x+1]!='0'){unidades2(num,x+1);r=false;}else{cout<<"diez"<<" ";}break;
 case '2':cout<<"veinte";if(num[x+1]!='0'){cout<<" y"<<" ";}break;
 case '3':cout<<"treinta";if(num[x+1]!='0'){cout<<" y"<<" ";}break;
 case '4':cout<<"cuarenta";if(num[x+1]!='0'){cout<<" y"<<" ";}break;
 case '5':cout<<"cincuenta";if(num[x+1]!='0'){cout<<" y"<<" ";}break;
 case '6':cout<<"sesenta";if(num[x+1]!='0'){cout<<" y"<<" ";}break;
 case '7':cout<<"setenta";if(num[x+1]!='0'){cout<<" y"<<" ";}break;
 case '8':cout<<"ochenta";if(num[x+1]!='0'){cout<<" y"<<" ";}break;
 case '9':cout<<"noventa";if(num[x+1]!='0'){cout<<" y"<<" ";}break;
 }
 return r;
}
void centenas(char num[N],int x){
 switch(num[x]){
 case '1':(num[x+2]!='0')?cout<<"ciento"<<" ":cout<<"cien"<<" ";break;
 case '2':cout<<"doscientos"<<" ";break;
 case '3':cout<<"trescientos"<<" ";break;
 case '4':cout<<"cuatrocientos"<<" ";break;
 case '5':cout<<"quinientos"<<" ";break;
 case '6':cout<<"seiscientos"<<" ";break;
 case '7':cout<<"setecientos"<<" ";break;
 case '8':cout<<"ochocientos"<<" ";break;
 case '9':cout<<"novecientos"<<" ";break;

 }
}
void miles(char num[N],int x){
 switch(num[x]){
 case '1':cout<<"mil"<<" ";break;
 case '2':cout<<"dos mil"<<" ";break;
 case '3':cout<<"tres mil"<<" ";break;
 case '4':cout<<"cuatro mil"<<" ";break;
 case '5':cout<<"cinco mil"<<" ";break;
 case '6':cout<<"seis mil"<<" ";break;
 case '7':cout<<"siete mil"<<" ";break;
 case '8':cout<<"ocho mil"<<" ";break;
 case '9':cout<<"nueve mil"<<" ";break;
 }
}
bool dec_miles(char num[N],int x){
 bool r=true;
 switch(num[x]){
 case '1':if(num[x+1]!='0'){unidades2(num,x+1);r=false;cout<<"mil ";}else{cout<<"diez mil"<<" ";}break;
 case '2':cout<<"veinte";if(num[x+1]!='0'){cout<<" y"<<" ";}else{cout<<" mil ";}break;
 case '3':cout<<"treinta";if(num[x+1]!='0'){cout<<" y"<<" ";}else{cout<<" mil ";}break;
 case '4':cout<<"cuarenta";if(num[x+1]!='0'){cout<<" y"<<" ";}else{cout<<" mil ";}break;
 case '5':cout<<"cincuenta";if(num[x+1]!='0'){cout<<" y"<<" ";}else{cout<<" mil ";}break;
 case '6':cout<<"sesenta";if(num[x+1]!='0'){cout<<" y"<<" ";}else{cout<<" mil ";}break;
 case '7':cout<<"setenta";if(num[x+1]!='0'){cout<<" y"<<" ";}else{cout<<" mil ";}break;
 case '8':cout<<"ochenta";if(num[x+1]!='0'){cout<<" y"<<" ";}else{cout<<" mil ";}break;
 case '9':cout<<"noventa";if(num[x+1]!='0'){cout<<" y"<<" ";}else{cout<<" mil ";}break;
 }
 return r;
}
void cent_dmiles(char num[N],int x){
 centenas(num,x);
}
void millones(char num[N],int x){
 switch(num[x]){
 case '1':cout<<"un millon";break;
 default: if(num[x]!='0'){unidades(num,x);if(num[x-1]!='0')cout<<" millones ";}break;
 }
}
bool decenas_mill(char num[N],int x){
 bool r=true;
 switch(num[x]){
 case '1':if(num[x+1]!='0'){unidades2(num,x+1);r=false;cout<<"millones ";}else{cout<<"diez millones"<<" ";}break;
 case '2':cout<<"veinte";if(num[x+1]!='0'){cout<<" y"<<" ";}else{cout<<" millones ";}break;
 case '3':cout<<"treinta";if(num[x+1]!='0'){cout<<" y"<<" ";}else{cout<<" millones ";}break;
 case '4':cout<<"cuarenta";if(num[x+1]!='0'){cout<<" y"<<" ";}else{cout<<" millones ";}break;
 case '5':cout<<"cincuenta";if(num[x+1]!='0'){cout<<" y"<<" ";}else{cout<<" millones ";}break;
 case '6':cout<<"sesenta";if(num[x+1]!='0'){cout<<" y"<<" ";}else{cout<<" millones ";}break;
 case '7':cout<<"setenta";if(num[x+1]!='0'){cout<<" y"<<" ";}else{cout<<" millones ";}break;
 case '8':cout<<"ochenta";if(num[x+1]!='0'){cout<<" y"<<" ";}else{cout<<" millones ";}break;
 case '9':cout<<"noventa";if(num[x+1]!='0'){cout<<" y"<<" ";}else{cout<<" millones ";}break;
 }
 return r;
}
void cent_mill(char num[N],int x){
 centenas(num,x);if(num[x+1]=='0')if(num[x+2]=='0')cout<<"millones ";
}
void gotoxy(int x, int y){
 COORD coord={x,y};
 SetConsoleCursorPosition(GetStdHandle(STD_OUTPUT_HANDLE), coord);
} 

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