9.s.2

#include <iostream>
#include <string>
#include <fstream>
using namespace std;

bool isDigits(string& s, int from, int to) {
    for (int i = from; i <= to; i++)
        if (!isdigit(s.at(i)))
            return false;
    return true;
}

bool isTNumber(string& word) {
    int lenght = word.length();
    if (lenght < 7 || lenght > 9)
        return false;

    switch (lenght) {
    case 7: // xxx-xxx
        return isDigits(word, 0, 2) && isDigits(word, 4, 6) && word[3] == '-';
    case 9: // xxx-xx-xx
        return isDigits(word, 0, 2) && isDigits(word, 4, 5) && word[3] == '-' && isDigits(word, 7, 8) && word[6] == '-';
    case 8: // xx-xx-xx
        return isDigits(word, 0, 1) && isDigits(word, 4, 5) && word[2] == '-' && isDigits(word, 6, 7) && word[5] == '-';
    default:
        return false;
    }
}

int main() {
    ifstream in ("f1.txt");
    ofstream out("f2.txt");

    string temp;

    while (in)
        if (in >> temp && isTNumber(temp))
            out << temp << endl;
    in.close();
    out.close();
}