# Levenshtein Distance + LCS 算法计算两个字符串的相似度

2016/12/29 15:39

``````//LD最短编辑路径算法
public static int LevenshteinDistance(string source, string target)
{
int cell = source.Length;
int row = target.Length;
if (cell == 0)
{
return row;
}
if (row == 0)
{
return cell;
}
int[, ] matrix = new int[row + 1, cell + 1];
for (var i = 0; i <= cell; i++)
{
matrix[0, i] = i;
}
for (var j = 1; j <= row; j++)
{
matrix[j, 0] = j;
}
var tmp = 0;
for (var k = 0; k < row; k++)
{
for (var l = 0; l < cell; l++)
{
if (source[l].Equals(target[k]))
tmp = 0;
else
tmp = 1;
matrix[k + 1, l + 1] = Math.Min(Math.Min(matrix[k, l] + tmp, matrix[k + 1, l] + 1), matrix[k, l + 1] + 1);
}
}
return matrix[row, cell];
}

//LCS最大公共序列算法
public static int LongestCommonSubsequence(string source, string target)
{
if (source.Length == 0 || target.Length == 0)
return 0;
int len = Math.Max(target.Length, source.Length);
int[, ] subsequence = new int[len + 1, len + 1];
for (int i = 0; i < source.Length; i++)
{
for (int j = 0; j < target.Length; j++)
{
if (source[i].Equals(target[j]))
subsequence[i + 1, j + 1] = subsequence[i, j] + 1;
else
subsequence[i + 1, j + 1] = 0;
}
}
int maxSubquenceLenght = (from sq in subsequence.Cast < int > () select sq).Max < int > ();
return maxSubquenceLenght;
}

//计算两个字符串相似度 数值越大越相似
public static float StringSimilarity(string source, string target)
{
var ld = LevenshteinDistance(source, target);
var lcs = LongestCommonSubsequence(source, target);
return ((float)lcs)/(ld+lcs);;
}``````
``````/// <summary>
/// 获取两个字符串的相似度(适合中文)
/// </summary>
/// <param name=”sourceString”>第一个字符串</param>
/// <param name=”str”>第二个字符串</param>
/// <returns></returns>
public static double SimilarityWith(string sourceString, string str)
{
char[] ss = sourceString.ToCharArray();
char[] st = str.ToCharArray();
int t = 0; //命中
int k = 0; //非命中
foreach (var item in st)
{
if (ss.Contains(item))
{
t++;
}
else
{
k++;
}
}
return (double)t / ((double)k + (double)t);
}``````

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