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POBest way to detect similar email addresses?
 

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  1. POBest way to detect similar email addresses?
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    <p>I have a list of ~20,000 email addresses, some of which I know to be fraudulent attempts to get around a "1 per e-mail" limit, such as username1@gmail.com, username1a@gmail.com, username1b@gmail.com, etc. I want to find similar email addresses for evaluation. Currently I'm using a Levenshtein algorithm to check each e-mail against the others in the list and report any with an edit distance of less than 2. However, this is painstakingly slow. Is there a more efficient approach?</p> <p>The test code I'm using now is:</p> <pre><code>using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.IO; using System.Threading; namespace LevenshteinAnalyzer { class Program { const string INPUT_FILE = @"C:\Input.txt"; const string OUTPUT_FILE = @"C:\Output.txt"; static void Main(string[] args) { var inputWords = File.ReadAllLines(INPUT_FILE); var outputWords = new SortedSet&lt;string&gt;(); for (var i = 0; i &lt; inputWords.Length; i++) { if (i % 100 == 0) Console.WriteLine("Processing record #" + i); var word1 = inputWords[i].ToLower(); for (var n = i + 1; n &lt; inputWords.Length; n++) { if (i == n) continue; var word2 = inputWords[n].ToLower(); if (word1 == word2) continue; if (outputWords.Contains(word1)) continue; if (outputWords.Contains(word2)) continue; var distance = LevenshteinAlgorithm.Compute(word1, word2); if (distance &lt;= 2) { outputWords.Add(word1); outputWords.Add(word2); } } } File.WriteAllLines(OUTPUT_FILE, outputWords.ToArray()); Console.WriteLine("Found {0} words", outputWords.Count); } } } </code></pre> <p><strong>Edit:</strong> Some of the stuff I'm trying to catch looks like:</p> <p>01234567890@gmail.com<br> 0123456789@gmail.com<br> 012345678@gmail.com<br> 01234567@gmail.com<br> 0123456@gmail.com<br> 012345@gmail.com<br> 01234@gmail.com<br> 0123@gmail.com<br> 012@gmail.com </p>
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    1. COWhat happens when you have two similar emails that belong to two different people?
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    2. COThat's why I'm providing the list to a human for evaluation purposes after...
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    3. COIf you run the code only when people try to make a new account, then it will cost you `O(n)` as opposed to `O(n^2)`.
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