This program creates a new file with the intersection of the words of two input files.

Intersection

/*
  Copyright (C) 2015  Katerine Muñoz Tello <[email protected]>

  This program is free software: you can redistribute it and/or modify
  it under the terms of the GNU General Public License as published by
  the Free Software Foundation, either version 3 of the License, or
  (at your option) any later version.

  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.

  You should have received a copy of the GNU General Public License
  along with this program.  If not, see <http://www.gnu.org/licenses/>.

*** Nombre: Katerine Muñoz Tello.
*** Objetivo:  Genere un nuevo archivo que contenga la intersección de palabras de ambos archivos.
*** SO: Ubuntu 15.04
*** IDE: Sublime text 3.
*** Compilador: gcc version 4.9.2 (Ubuntu 4.9.2-10ubuntu13).
*/

#include <iostream>
#include <string>
#include <fstream>
#include <stdlib.h>
using namespace std;

void crearArchivoSalida(string palabra, ifstream &file);  // Crea el archivo con las intersecciones.
int Iguales(string palabra, ifstream &file);              // Verifica las palabras iguales.


int main(){
  string palabra;

  ifstream texto1;
  ifstream texto2;

  texto1.open("texto3.txt");
  texto2.open("texto4.txt");

  if(texto1.fail() && texto2.fail()){
    cout << "El archivo no existe.";
    system("PAUSE");
    exit (1);
  }
  else{
    while(texto1 >> palabra){
      crearArchivoSalida(palabra, texto2);
    }
  }

  texto1.close();
  texto2.close();
  return 0;
} 


int Iguales(string palabra, ifstream &file){
  string palabra2;
  int cumple = 0;

  file.clear();
  file.seekg(0, ios::beg);
 
  while(file >> palabra2){
    if(palabra == palabra2){
      cumple = 1;
    }
  }
  return cumple;
}

void crearArchivoSalida(string palabra, ifstream &file){
  int existe = 0;
  string palabra2, p3;
  fstream newfile;
  newfile.open("texto_interseccion.txt", ios::in);

  existe = Iguales(palabra, file);

  while(newfile >> p3){
    if(palabra == p3){
      existe = 0;
    }
  }
  if(existe == 1){
    newfile.close();
    newfile.open("texto_interseccion.txt", ios::app);
  	newfile << palabra << "\t";
  }
 
  newfile.close();
}

Disclaimer

I know is a really bad habit for me to code in both spanish and english (as you may see, there're variables on those languages) BUT I'm coding in C++ since the begining of the year, so, excuse me please :)