Data commit

Task/Permutations/Erlang/permutations-1.erl

@@ -0,0 +1,5 @@
+-module(permute).
+-export([permute/1]).
+
+permute([]) -> [[]];
+permute(L) -> [[X|Y] || X<-L, Y<-permute(L--[X])].

Task/Permutations/Erlang/permutations-2.erl

@@ -0,0 +1 @@
+F = fun(L) -> G = fun(_, []) -> [[]]; (F, L) -> [[X|Y] || X<-L, Y<-F(F, L--[X])] end, G(G, L) end.

Task/Permutations/Erlang/permutations-3.erl

@@ -0,0 +1,18 @@
+-module(permute).
+
+-export([permute/1]).
+
+permute([]) -> [[]];
+permute(L) -> zipper(L, [], []).
+
+% Use zipper to pick up first element of permutation
+zipper([], _, Acc) -> lists:reverse(Acc);
+zipper([H|T], R, Acc) ->
+  % place current member in front of all permutations
+  % of rest of set - both sides of zipper
+  prepend(H, permute(lists:reverse(R, T)),
+    % pass zipper state for continuation
+    T, [H|R], Acc).
+
+prepend(_, [], T, R, Acc) -> zipper(T, R, Acc); % continue in zipper
+prepend(X, [H|T], ZT, ZR, Acc) -> prepend(X, T, ZT, ZR, [[X|H]|Acc]).

Task/Permutations/Erlang/permutations-4.erl

@@ -0,0 +1 @@
+main(_) -> io:fwrite("~p~n", [permute:permute([1,2,3])]).