코딜리티 레슨1 Iterations - A binary gap

문제

 

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); }

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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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​→ 결론은 양옆이 1로 막혀있는 0의 최대 갯수를 출력하라.

 

 

답변

 

1. 처음에는 0의 갯수를 하나하나 세는 방법을 했다.

2. 1과 1사이에 있는 0의 갯수를 세기로 변경

3. 알고리즘은 수학이다로 생각 번경

4. 이클립스에 작업을 하고 옮기는 형식으로 진행했다.

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class Solution {
    public int solution(int N) {
        // write your code in Java SE 8
        String binary = Integer.toBinaryString(N);
        
        int start = binary.indexOf("1");
        int end = binary.lastIndexOf("1");
        
        String newBinary = binary.substring(start, end+1);
        String[] arr = newBinary.split("1");
        int max = 0;
        
        for(String a : arr) {
            if(a.length() > max) {
                max = a.length();
            }
        }
        
        return max;
    }
}

 

결과

 

https://app.codility.com/demo/results/trainingCYM38E-HDN/