Dart Dare - Secret Santas

gistfile1.dart

import 'dart:io';

void main() {
  var input = '''
  Zoe Washburne
  Hoban Washburne
  Malcolm Reynolds
  Simon Tam
  River Tam
  Buffy Summers
  Dawn Summers''';
  
  Map<String, List<String>> people = new Map<String, List<String>>();
  Map<String, List<String>> schizoPeople = new Map<String, List<String>>();

  input.split("\n").forEach((s) {
    var p = s.trim().split(" ");
    if(people[p[1]] == null) { 
      people[p[1]] = new List<String>();
      schizoPeople[p[1]] = new List<String>();
    }
    people[p[1]].add(p[0]);
    schizoPeople[p[1]].add(p[0]);
  });

  people.forEach((k, v) => people = Match(people, false));
  schizoPeople.forEach((k, v) => schizoPeople = Match(schizoPeople, true));
}

Map<String, List<String>> Match(Map<String, List<String>> people, bool newLine) {
  for(var family in people.keys) {
    if(people[family].isNotEmpty) {
      stdout.write(people[family].removeLast() + " " + family);
      if(newLine) {
        print("");
        newLine = false;
      } else {
        stdout.write(", ");
        newLine = true;
      }
    }
  }
  
  return people;
}

Thanks for sharing! BTW you can use print() instead of stdout.write. It's a bit shorter, and print works in the browser, too.