Reversed String by Words [File Method]

// cpp program : reversed string by words [file method]
// AIUB SUMMER"15-16" FINAL CODEWRITING QUES.01
// Author: HTA

#include <iostream>
#include <fstream>
#include <conio.h>

using namespace std;

int word_number(string);

int main() {
    string str;
    cout << "String from User: "; getline(cin,str);
    ofstream write; write.open("input.txt");
    write << str << endl; write.close();
    int words=word_number(str);
    ifstream read("input.txt");
    string str2[words];
    for (int j=(words-1);true;j--) {
        read >> str2[j];
        if(read.eof()) break;
    }
    read.close(); string str3;
    for (int j=0;j<words;j++) {
        str3+=(str2[j]+" ");
    }
    write.open("reverseOutput.txt");
    write << str3 << endl; write.close();
    cout << "Reversed string: " << str3 << endl;
    getch();
    return 0;
}

int word_number(string st) {
    int counta = 0;
    for (int i = 0; st[i]; i++)
        if (st[i] == ' ')
            counta++;
    if (st[0] != '\0' && st[0] != ' ') counta++;
    return counta;
}