Levenshtein Distance

Levenshtein distance is a string metric for measuring the difference between two sequences. Informally, the Levenshtein distance between two words is the minimum number of single-character edits (i.e. insertions, deletions or substitutions) required to change one word into the other. It is named after Vladimir Levenshtein, who considered this distance in 1965.

private static uint MIN3(uint a, uint b, uint c)
{
return ((a) < (b) ? ((a) < (c) ? (a) : (c)) : ((b) < (c) ? (b) : (c)));
}

public static int LevenshteinDistance(string s1, string s2)
{
uint s1len, s2len, x, y, lastdiag, olddiag;
s1len = (uint)s1.Length;
s2len = (uint)s2.Length;
uint[] column = new uint[s1len + 1];

for (y = 1; y <= s1len; ++y)
column[y] = y;

for (x = 1; x <= s2len; ++x)
{
column = x;

for (y = 1, lastdiag = x - 1; y <= s1len; ++y)
{
olddiag = column[y];
column[y] = MIN3(column[y] + 1, column[y - 1] + 1, (uint)(lastdiag + (s1[(int)(y - 1)] == s2[(int)(x - 1)] ? 0 : 1)));
lastdiag = olddiag;
}
}

return (int)(column[s1len]);
}

Example

int result = LevenshteinDistance("kitten", "sitting");

Output

result: 3