get a list, and jump n[i] positions to next element until out of index, In a time complexity of O(N)

task.erl

-module(var1).
-author("Sergio Veiga <[email protected]>").

% get a list, and jump n[i] positions to next element until out of index
% In a time complexity of O(N)
% Has the graph loops?
% How many jumps to destination?

-export([
  calculate_jumps/1,
  test/0
]).


-spec calculate_jumps([integer()]) -> {ok, pos_integer()} | never.
calculate_jumps(A) ->
  F = fun()->Numbers = list_to_tuple(A),loop(0, 1, Numbers) end,
  {T,Res} = timer:tc(F),
  io:format("In T:~p Res:~p\n",[T,Res]).


loop(Jumps, Position,_) when Position < 1 ->
  { ok, Jumps };
loop(Jumps, Position, Numbers) when Position > size(Numbers) ->
  { ok, Jumps };
loop(Jumps, _, Numbers) when Jumps > size(Numbers) ->
  never;

loop(Jumps, Position, Numbers) ->
  El = element(Position, Numbers),
  NewPosition = Position + El,
  loop(Jumps+1, NewPosition, Numbers).

test() ->
  { ok, 4 } = calculate_jumps([2,3,-1,1,3]),
  never = calculate_jumps([1,1,-1,1]),
  ok.