boyer-moore

StringUtils.contains of Apache and Boyer–Moore string search algorithm

由 安稳与你 提交于 2020-01-03 17:43:36
问题 To search for s in S (size(S) >= size(s) and return a true/false value), it's better for performance to use StringUtils.contains() of Apache or use Boyer-Moore algorithm implemented and tested well by someone I found? Thanks 回答1: The last time I looked into the Java regex matching code while debugging, the Java 7 regex engine used the Boyer-Moore algorithm for sequences of literal text matches. So the easiest way to find a String using Boyer-Moore is to prepare using p=Pattern.compile

Boyer-Moore Practical in C#?

由 一笑奈何 提交于 2019-12-31 08:28:07
问题 Boyer-Moore is probably the fastest non-indexed text-search algorithm known. So I'm implementing it in C# for my Black Belt Coder website. I had it working and it showed roughly the expected performance improvements compared to String.IndexOf() . However, when I added the StringComparison.Ordinal argument to IndexOf , it started outperforming my Boyer-Moore implementation. Sometimes, by a considerable amount. I wonder if anyone can help me figure out why. I understand why StringComparision

Boyer Moore Algorithm Implementation?

由 送分小仙女□ 提交于 2019-12-22 10:55:42
问题 Is there a working example of the Boyer-Moore string search algorithm in C? I've looked at a few sites, but they seem pretty buggy, including wikipedia. Thanks. 回答1: The best site for substring search algorithms: http://igm.univ-mlv.fr/~lecroq/string/ 回答2: There are a couple of implementations of Boyer-Moore-Horspool (including Sunday's variant) on Bob Stout's Snippets site. Ray Gardner's implementation in BMHSRCH.C is bug-free as far as I know 1 , and definitely the fastest I've ever seen or

Difference between original Boyer–Moore and Boyer–Moore–Horspool Algorithm [closed]

由 微笑、不失礼 提交于 2019-12-22 01:11:34
问题 Closed . This question needs to be more focused. It is not currently accepting answers. Want to improve this question? Update the question so it focuses on one problem only by editing this post. Closed 2 years ago . I am not able to understand the changes which Horspool made in his algorithm. If you have any link of Boyer–Moore–Horspool algorithm then please do tell me. 回答1: Here are my few observations: BM: Preprocessing complexity: Θ(m + σ) Worst Case : Θ(nm) If pattern exists Θ(n+m) If

Boyer-Moore-Horspool Algorithm for All Matches (Find Byte array inside Byte array)

由 北城以北 提交于 2019-12-18 12:33:04
问题 Here is my implementation of BMH algorithm (it works like a charm): public static Int64 IndexOf(this Byte[] value, Byte[] pattern) { if (value == null) throw new ArgumentNullException("value"); if (pattern == null) throw new ArgumentNullException("pattern"); Int64 valueLength = value.LongLength; Int64 patternLength = pattern.LongLength; if ((valueLength == 0) || (patternLength == 0) || (patternLength > valueLength)) return -1; Int64[] badCharacters = new Int64[256]; for (Int64 i = 0; i < 256;

Is there a Boyer-Moore string search and fast search and replace function and fast string count for Delphi 2010 String (UnicodeString) out there?

由 岁酱吖の 提交于 2019-12-17 17:32:18
问题 I need three fast-on-large-strings functions: fast search, fast search and replace, and fast count of substrings in a string. I have run into Boyer-Moore string searches in C++ and Python, but the only Delphi Boyer-Moore algorithm used to implement fast search and replace that I have found is part of the FastStrings by Peter Morris, formerly of DroopyEyes software, and his website and email are no longer working. I have already ported FastStrings forward to work great for AnsiStrings in

Seeking Unicode-savvy function for searching text in binary data

由 隐身守侯 提交于 2019-12-14 03:24:49
问题 I need to find unicode text inside binary data (files). I'm seeking any C or C++ code or library that I can use on macOS. Since I guess this is also useful to other platforms, so I rather make this question not specific to macOS. On macOS, the NSString functions, meeting my unicode savvyness needs, can't be used because they do not work on binary data. As an alternative I've tried the POSIX complient regex functions provided on macOS, but they have some limitations: They are not normalization

How to implement string matching algorithm with Hadoop?

由 跟風遠走 提交于 2019-12-13 09:10:19
问题 I want to implement a string matching(Boyer-Moore) algorithm using Hadoop. I just started using Hadoop so I have no idea how to write a Hadoop program in Java. All the sample programs that I have seen so far are word counting examples and I couldn't find any sample programs for string matching. I tried searching for some tutorials that teaches how to write Hadoop applications using Java but couldn't find any. Can you suggest me some tutorials where I can learn how to write Hadoop applications

字符串匹配的Boyer-Moore算法

由 杀马特。学长 韩版系。学妹 提交于 2019-12-10 00:05:30
上一篇文章，我介绍了 KMP算法 。 但是，它并不是效率最高的算法，实际采用并不多。各种文本编辑器的"查找"功能（Ctrl+F），大多采用 Boyer-Moore算法 。 Boyer-Moore算法不仅效率高，而且构思巧妙，容易理解。1977年，德克萨斯大学的Robert S. Boyer教授和J Strother Moore教授发明了这种算法。 下面，我根据Moore教授自己的 例子 来解释这种算法。 1. 假定字符串为"HERE IS A SIMPLE EXAMPLE"，搜索词为"EXAMPLE"。 2. 首先，"字符串"与"搜索词"头部对齐，从尾部开始比较。 这是一个很聪明的想法，因为如果尾部字符不匹配，那么只要一次比较，就可以知道前7个字符（整体上）肯定不是要找的结果。 我们看到，"S"与"E"不匹配。这时， "S"就被称为"坏字符"（bad character），即不匹配的字符。 我们还发现，"S"不包含在搜索词"EXAMPLE"之中，这意味着可以把搜索词直接移到"S"的后一位。 3. 依然从尾部开始比较，发现"P"与"E"不匹配，所以"P"是"坏字符"。但是，"P"包含在搜索词"EXAMPLE"之中。所以，将搜索词后移两位，两个"P"对齐。 4. 我们由此总结出 "坏字符规则" ： 　　后移位数 = 坏字符的位置 - 搜索词中的上一次出现位置 如果"坏字符

字符串匹配算法之"Boyer Moore"

由 柔情痞子 提交于 2019-12-09 23:49:23
Boyer-Moore字符串搜索算法是一种非常高效的字符串搜索算法。它由Bob Boyer和J Strother Moore设计于1977年，最初的定义1975年就给出了，后续才给出构造算法以及算法证明。 先假定部分定义： 1、pattern 为模式字符串，长度为patLen; 2、Text为目标查找字符串，长度为n; 2、当前不匹配字符在pattern中位置为 j（0≤ j ≤patLen -1）; 3、已经匹配的长度为 m（0≤ m ＜patLen）; 4、先假设不匹配字符在pattern中位置为 Δ(*),其中*可以是任何字符; 很多资料里面讲解原理时说的数组位置都是从1开始的，这里为了好理解code，都是从0开始; 首先来看下坏字符规则： 一、坏字符规则（ bad character rule ）： 让不匹配字符和pattern中最右边出现的该字符对齐匹配，如果没有则全部跳过； >假设1 ：遇到不匹配字符，如果该字符在pattern 中不存在，有:（如下图示跳转） 字符指针右移：patLen 长度 后和 pattern 右对齐; Pattern 右移：patLen – m; >假设2 ：遇到不匹配字符，如果该字符在pattern 中存在，这里也分两种情况: a>.在pattern最右边出现的该字符在当前不匹配字符左边, 有:（如下图示跳转） 字符指针右移：j–Δ(‘-’)
订阅 boyer-moore