diff --git a/algorithm/_sidebar.md b/algorithm/_sidebar.md index c49fea0..05b0223 100644 --- a/algorithm/_sidebar.md +++ b/algorithm/_sidebar.md @@ -1,3 +1,4 @@ - [下一个斐波拉契数](/algorithm/next-fibonacci-number.md) - [一个字符串包裹函数](/algorithm/a-word-wrap-functionality.md) -- [打印 100 以内的素数](/algorithm/prime-numbers-from-1-to-100.md) \ No newline at end of file +- [打印 100 以内的素数](/algorithm/prime-numbers-from-1-to-100.md) +- [二进制空白](/algorithm/binary-gap.md) \ No newline at end of file diff --git a/algorithm/binary-gap.md b/algorithm/binary-gap.md new file mode 100644 index 0000000..de01f6e --- /dev/null +++ b/algorithm/binary-gap.md @@ -0,0 +1,127 @@ +# Binary Gap(二进制空白) + +> 🔔 参与讨论:https://www.isharkfly.com/t/binary-gap/311 + + +**英文描述** + +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]. + +**中文描述** + +这里我不按照原文一字一字的翻译,但是尽量按照题目的要求把题目解释清楚。 + +这里题目的要求是,将 N 为一个整数类型的数据,转换为一个 2 进制的字符串,然后在返回的字符串中返回最大的 0 的间隔数字。 + +例如 529 转换为 2 进制的字符串为:1000010001,在这里,将会存在以 1 为分割的字符串 0000 和 000,这 2 个字符串的长度分别为 4 和 +3。 + +我们的算法需要返回的值为 4。 + +### 思路和点评 + +这个题目的思路其实比较简单,你需要首先将 N 这个整数,转换为 0 和 1 的字符串。然后在转换成功的字符串中返回以 1 分分割的 0 +的长度。 + +这里可能需要考虑下面的几种情况。 + +| 情况 | 结果 | +|----|---------------------------------| +| 11 | 这个情况应该返回的长度为 0 | +| 10 | 这个情况因为没有被 1 这个字符串封闭,因此应该返回长度为 0 | + +传统的思路应该是采取字符串分割的方式,进行遍历后获得结果。 + +我们在这里采取一种相对不是非常常规的方式,例如在 10000010001 字符串中插入 #,将字符串变为 #1#00000#1#000#1#。 + +然后将字符串按照 1 进行分割,那么分割后的数组应该分别存储的数据为:#,#0000#,#000#,# + +这里我们只需要找到 #...# 中值最大的连续 0 字符串就可以了。基本上可以使用 1 个字符串替换函数和一个字符串分割函数就可以了,并不需要多次存储和遍历。 + +**源代码** + +源代码和有关代码的更新请访问 GitHub: + +https://github.com/cwiki-us/java-tutorial/blob/master/src/test/java/com/ossez/lang/tutorial/tests/codility/CodilityBinaryGapTest.java + +代码思路请参考: + +```java +package com.ossez.lang.tutorial.tests.codility; + +import org.junit.Test; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +/** + *

+ * More details about question see link below + *

+ *

+ * + * @author YuCheng + * + */ +public class CodilityBinaryGapTest { + + private final static Logger logger = LoggerFactory.getLogger(CodilityBinaryGapTest.class); + + /** + * + */ + @Test + public void testMain() { + logger.debug("BEGIN"); + + int N = 529; + String intStr = Integer.toBinaryString(N); + + intStr = intStr.replace("1", "#1#"); + + String[] strArray = intStr.split("1"); + + int maxCount = 0; + for (int i = 0; i < strArray.length; i++) { + String checkStr = strArray[i]; + int countLength = 0; + + if (checkStr.length() > 2 && checkStr.startsWith("#") && checkStr.endsWith("#")) { + checkStr = checkStr.replace("#", ""); + countLength = checkStr.length(); + + if (maxCount < countLength) { + maxCount = countLength; + } + + } + } + + logger.debug("MAX COUNT: [{}]", maxCount); + } + +} +``` \ No newline at end of file