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fix RatcliffObershelpSimilarity at ("abab","ababab") case #8

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fix RatcliffObershelpSimilarity at ("abab","ababab") case #8

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53 changes: 51 additions & 2 deletions FuzzyString/RatcliffObershelpSimilarity.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -10,7 +10,56 @@ public static partial class ComparisonMetrics
{
public static double RatcliffObershelpSimilarity(this string source, string target)
{
return (2 * Convert.ToDouble(source.Intersect(target).Count())) / (Convert.ToDouble(source.Length + target.Length));
var matchs = GetMatchQueue(source, target);
return 2.0 * matchs.Select(match => match.Length).Sum() / (source.Length + target.Length);
}

private static List<string> GetMatchQueue(string source, string target)
{
List<string> list = new List<string>();
var match = FrontMaxMatch(source, target);
if (match.Length > 0)
{
var frontSource = source.Substring(0, source.IndexOf(match));
var frontTarget = target.Substring(0, target.IndexOf(match));
var frontQueue = GetMatchQueue(frontSource, frontTarget);

var endSource = source.Substring(source.IndexOf(match) + match.Length);
var endTarget = target.Substring(target.IndexOf(match) + match.Length);
var endQueue = GetMatchQueue(endSource, endTarget);

list.Add(match);
list.AddRange(frontQueue);
list.AddRange(endQueue);
return list;
}
else
{
return list;
}
}

private static string FrontMaxMatch(string a, string b)
{
var index = 0;
var length = 0;

for (int i = 0; i < a.Length; i++)
{
Enumerable.Range(1, a.Length - i)
.ToList()
.ForEach
(len =>
{
if (len > length && b.Contains(a.Substring(i, len)))
{
index = i;
length = len;
}
});
}

return a.Substring(index, length);
}
}
}
}