Levenshtein Distance

LevenshteinDistance
the Levenshtein distance is a metric for measuring the amount of difference between two sequences (i.e., the so called edit distance). The Levenshtein distance between two strings is given by the minimum number of operations needed to transform one string into the other, where an operation is an insertion, deletion, or substitution of a single character.

int LevenshteinDistance(char s[1..m], char t[1..n])
   // d is a table with m+1 rows and n+1 columns
   declare int d[0..m, 0..n]
   for i from 0 to m
       d[i, 0] := i
   for j from 0 to n
       d[0, j] := j
   for i from 1 to m
       for j from 1 to n
       {
           if s[i] = t[j] then cost := 0
                          else cost := 1
           d[i, j] := minimum(
                                d[i-1, j] + 1,     // deletion
                                d[i, j-1] + 1,     // insertion
                                d[i-1, j-1] + cost   // substitution
                            )
       }
   return d[m, n]

http://www.merriampark.com/ld.htm
http://en.wikipedia.org/wiki/Levenshtein_distance