My solution to the first Dart Dare (https://plus.google.com/u/0/+SethLadd/posts/XjgFRvqtVA4)

secretsanta.dart

import 'dart:math';

void main() {
  List<String> names = '''
Zoe Washburne
Hoban Washburne
Malcolm Reynolds
Simon Tam
River Tam
Buffy Summers
Dawn Summers'''.split("\n");
  
  last_names_match(pair) {
    var last_names = pair.map((name) => name.split(" ").last);
    return last_names.first == last_names.last;
  }
  
  names_match(pair) {
    return pair.first == pair.last;
  }
  
  candidate_matches_pick(pick, candidate) {
    return pick != null && (pick.first == candidate.first || pick.last == candidate.last);
  }
  
  can_swap_pick_with_name(pick, name, missing_name) {
    return pick.last != name && pick.first.split(" ").last != name.split(" ").last && pick.first != missing_name && pick.first.split(" ").last != missing_name.split(" ").last;
  }
  
  pick_names(List names) {
    var random = new Random();
  
    List candidates = names.map((name) => names.map((n) => [name, n])).expand((i) => i).toList()..removeWhere(names_match)..removeWhere(last_names_match);
    candidates.shuffle(random);
    List<List> picks = names.map((name) {
      var pick = candidates.firstWhere((candidate) => candidate.first == name, orElse: () => [name, null]);
      candidates.removeWhere((candidate) => candidate_matches_pick(pick, candidate));
      return pick;
    }).toList();
    
    // Handle the case where the last person ran out of picks
    // This happens if the only name left was themselves, or if the remaining name was excluded because of their last name
    if (picks.last.last == null) {
      var bad_pick = picks.last;
      var missing_name = names.toSet().difference(picks.map((pick) => pick.last).toSet()).first;
      var swappable_pick = picks.firstWhere((pick) => can_swap_pick_with_name(pick, bad_pick.first, missing_name));
      
      bad_pick[1] = swappable_pick.last;
      swappable_pick[1] = missing_name;
    }
    
    return picks;
  }
  
  var picks = pick_names(names);
  
  picks.forEach((pick) {
    print("${pick.first} is buying a gift for ${pick.last}.");
  });
}