Question

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. E.g.: 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. Write a function: class Solution { public int binary_gap(int 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.

Answer 1

This is the best way:

class Solution { public static int solution(int N) { return Optional.ofNullable(N) .map(Integer::toBinaryString) .filter(n -> n.length() > 1) .map(t -> { List<Integer> counts = new ArrayList<>(); int count = 0; for(int i = 0; i < t.length(); i++) { if(t.charAt(i) == '0') { count += 1; } else if(count > 0) { counts.add(count); count = 0; } } if(counts.size() > 0) { Collections.sort(counts); return counts.get(counts.size() - 1); } return 0; }) .orElse(0); }}