Dart implementation for Filter Duplicate numbers

main.dart

void main() {
  /// Mock list of contacts
  final _rawContacts = [
    // Actual Number: 9000000000
    "+919000000000",
    "+9190000 00000",
    "+91900-000-0000",
    "919000000000",
    "9190000 00000",
    "91900-000-0000",
    "9000000000",
    "90000 00000",
    "900-000-0000",
    
    // Actual Number: 9000000015
    "+919000000015",
    "+9190000 00015",
    "+91900-000-0015",
    
    // Actual Number: 9100000000
    "919100000000",
    "9191000 00000",
    "91910-000-0000",
    "9900000000",
    "99000 00000",
    "990-000-0000",
    
    // invalid numbers
    "99000002",
    "9900 0009",
    "9900-0008",
  ];

  //print(_rawContacts);

  final _filtered = _rawContacts.map((number) {
    final _processed = _removeSpecialSymbols(number);
    final _actualNumber = _getActualNumber(_processed);
    return _actualNumber;
  }).toSet()..removeWhere((number) => number.isEmpty);

  print(_filtered);
}

/// Removes +,- & whitespaces from the numbers
String _removeSpecialSymbols(String number) {
  final _result =
      number.replaceAll('+', '').replaceAll('-', '').replaceAll(' ', '');
//   print('_removeSpecialSymbols: $_result');
  return _result;
}

/// strips extra digits or numbers from start of the string
String _getActualNumber(String number) {
  var _result = number;
  final _length = number.length;
  if (_length > 10) { // without country code
    final _diff = _length - 10;
    _result = number.substring(_diff, _length);
  } else {
    // invalid number return as empty string
    return '';
  }
//   print('_getActualNumber: $_result');
  return _result;
}