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55 lines
1.9 KiB
C#
55 lines
1.9 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Text;
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namespace FuzzyString
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{
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public static partial class ComparisonMetrics
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{
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public static int LevenshteinDistance(this string source, string target)
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{
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if (source.Length == 0) { return target.Length; }
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if (target.Length == 0) { return source.Length; }
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int distance = 0;
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if (source[source.Length - 1] == target[target.Length - 1]) { distance = 0; }
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else { distance = 1; }
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return Math.Min(Math.Min(LevenshteinDistance(source.Substring(0, source.Length - 1), target) + 1,
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LevenshteinDistance(source, target.Substring(0, target.Length - 1))) + 1,
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LevenshteinDistance(source.Substring(0, source.Length - 1), target.Substring(0, target.Length - 1)) + distance);
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}
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public static double NormalizedLevenshteinDistance(this string source, string target)
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{
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int unnormalizedLevenshteinDistance = source.LevenshteinDistance(target);
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return unnormalizedLevenshteinDistance - source.LevenshteinDistanceLowerBounds(target);
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}
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public static int LevenshteinDistanceUpperBounds(this string source, string target)
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{
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// If the two strings are the same length then the Hamming Distance is the upper bounds of the Levenshtien Distance.
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if (source.Length == target.Length) { return source.HammingDistance(target); }
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// Otherwise, the upper bound is the length of the longer string.
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else if (source.Length > target.Length) { return source.Length; }
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else if (target.Length > source.Length) { return target.Length; }
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return 9999;
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}
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public static int LevenshteinDistanceLowerBounds(this string source, string target)
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{
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// If the two strings are the same length then the lower bound is zero.
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if (source.Length == target.Length) { return 0; }
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// If the two strings are different lengths then the lower bounds is the difference in length.
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else { return Math.Abs(source.Length - target.Length); }
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}
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}
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}
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