[CODILITY] BinaryGap - Java

1. 문제

BinaryGap coding task - Learn to Code - Codility

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:

class Solution { public int solution(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.

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].

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2. 풀이

1과 1 사이에 있는 0 개수를 구하는 것이므로 1이 한번이라도 등장해야 0개수를 센다.

import java.util.*;

class Solution {
    public int solution(int N) {
        int answer = 0;

        int tmp = 0;
        boolean one = false;
        while(N>0){
            if(N%2==1){
                one = true;
                answer = Math.max(answer,tmp);
                tmp = 0;
            }else if(one){
                tmp++;
            }
            N/=2;
        }

        return answer;
    }
}

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3. 결과

처음부터 2분만에 푼 건 아니다! 16분만에 푼 게 있었는데 그 기록을 못찾아서 다시 풀었다.