I’m beating myself that I can’t figure it out, but if anybody could help me/guide me through I would really appreciate it.

So the problem itself:

```
A binary gap within a positive integer N is any maximal sequence of consecutive zeros that is surrounded by ones at both ends in the binary representation of N.
For example, number 9 has binary representation 1001 and contains a binary gap of length 2. The number 529 has binary representation 1000010001 and contains two binary gaps: one of length 4 and one of length 3. The number 20 has binary representation 10100 and contains one binary gap of length 1. The number 15 has binary representation 1111 and has no binary gaps. The number 32 has binary representation 100000 and has no binary gaps.
Write a function:
function solution(N);
that, given a positive integer N, returns the length of its longest binary gap. The function should return 0 if N doesn't contain a binary gap.
For example, given N = 1041 the function should return 5, because N has binary representation 10000010001 and so its longest binary gap is of length 5. Given N = 32 the function should return 0, because N has binary representation '100000' and thus no binary gaps.
Write an efficient algorithm for the following assumptions:
N is an integer within the range [1..2,147,483,647].
```

And my first approach was:

```
defmodule Codility1BinaryGap do
def largest_bg(number) do
# in if statement I was trying filter all binary reps where I have at least two "1"s
if Enum.count(Integer.digits(number, 2), fn x -> div(x, 1) == 1 end) >= 2 do
# converting int to binary string represenatation: for int 68 -> "1000100"
Integer.to_string(number, 2)
# splitting "1000100" -> ["", "000", "00"]
|> String.split("1")
# counting length of each x in ["", "000", "00"]
|> Enum.map(fn x -> String.length(x) end)
# getting max
|> Enum.max()
else
0
end
end
end
```

It is ugly and not sufficient, but it worked except the only case where the provided number is `20`

or `"10100"`

It has two `"1"`

s and it passing if statement, but it is returning, obviously `2`

instead of `1`

.

so, I’ve started differently using Enum.reduce where the main idea was:

```
acc = 0
#1.
if x == "0", do: acc + 1
#2.
if x == "1" -> need to insert acc to a list and reset acc to 0 and start over
#3.
at the end Enum.max() for the list where I stored everything
```

so having this simple example I can clearly see that acc collect `3`

and `2`

for `"1000100"`

:

```
defmodule Codility1BinaryGap do
def largest_bg(number) do
list = Integer.to_string(number, 2) |> String.graphemes()
Enum.reduce(list, 0, fn x, acc ->
if x == "0" do
(acc + 1) |> IO.inspect(label: "IF: \n")
else
0 |> IO.inspect(label: "ELSE: \n")
end
end)
end
end
```

```
ELSE:
: 0
IF:
: 1
IF:
: 2
IF:
: 3
ELSE:
: 0
IF:
: 1
IF:
: 2
```

So my question how properly insert acc to a list, reset it to zero and start over?

The solution is very easy in JS or Python since we can use and rebind variables

Thank you so much in advance for any possible help!