/* 

  Pair of socks in Picat.

  https://en.wikibooks.org/wiki/Puzzles/Logic_puzzles/Pair_of_Socks
  """
  There are 10 black socks and 10 white socks(no left-right distinction) in the 
  wardrobe. Your task is to draw the minimum number of socks at random to be 
  sure you have a pair of a single color.

  How many socks should you draw?
  """

  Here's a simple simulation of 100 runs

    [3,2,2,2,2,2,2,2,2,3,2,2,3,2,3,2,2,2,3,2,3,3,3,3,2,3,3,2,3,3,2,3,3,2,3,3,2,2,2,3,3,2,3,2,3,3,3,3,2,3,2,2,2,3,3,3,2,2,2,2,2,2,2,3,2,2,3,3,3,2,2,3,3,3,3,2,3,3,2,2,2,2,2,3,2,2,2,3,3,2,2,3,3,3,2,2,3,2,3,3]
    max = 3

  I.e. we need to draw 3 socks to be sure to get a pair of single socks.

  Yes, this is overkill...

  This program was created by Hakan Kjellerstrand, hakank@gmail.com
  See also my Picat page: http://www.hakank.org/picat/

*/

main => go.

go ?=>
  Socks = ["Black" : _ in 1..10] ++ ["White" : _ in 1..10],
  Len = Socks.len,
  println(socks=Socks),

  _ = random2(),
  Ls = [],
  foreach(_ in 1..100)
    Found = [],
    foreach(N in 1..Len, break(Found == true))
      Ks = get_k_random(N,1,Len),
      Rs = [ Socks[R] : R in Ks],
      Map = occurrences(Rs),
      if Map.get("Black",0) >= 2  ; Map.get("White",0) >= 2 then
        Ls := Ls ++ [N],
        Found := true
      end,
    end,
  end,
  println(Ls),
  println(max=Ls.max),
  nl.
go => true.

% Get k random unique numbers between From and To
get_k_random(K, From, To) = Ls =>
  Ls0 = [],
  while (Ls0.len < K)
    R = random(From,To),
    if not membchk(R,Ls) then
      Ls0 := Ls0 ++ [R]
    end
  end,
  Ls = Ls0.


%
% occurrences(List): 
% returns a map with all the keys and the 
% number of occurrences of each elements.
%
occurrences(List) = Map =>
  Map = new_map(),
  foreach(E in List)
     Map.put(E, cond(Map.has_key(E),Map.get(E)+1,1))
  end.