1-bit and 2-bit Characters

is_one_bit_character(Bits) ->
    is_one_bit_character(Bits, 0, length(Bits)).

% leetcode: 1-bit and 2-bit characters
% https://leetcode.com/problems/1-bit-and-2-bit-characters/description/
%
% we have two special characters:
% - one-bit character: represented by a single 0
% - two-bit character: represented by 10 or 11
%
% given a binary array bits that ends with 0, return true if the last character
% must be a one-bit character.
%
% approach: traverse from the start. if we see 0, it's a one-bit char (move 1).
% if we see 1, it's the start of a two-bit char (move 2). if we end up exactly
% at the last index, the last char is one-bit.

is_one_bit_character(_Bits, I, Len) when I >= Len - 1 ->
    I =:= Len - 1;
is_one_bit_character(Bits, I, Len) ->
    Bit = lists:nth(I + 1, Bits),
    if
        Bit =:= 0 -> is_one_bit_character(Bits, I + 1, Len);
        Bit =:= 1 -> is_one_bit_character(Bits, I + 2, Len)
    end.