Class LongestCommonSubsequence

java.lang.Object
info.debatty.java.stringsimilarity.LongestCommonSubsequence
All Implemented Interfaces:
StringDistance, Serializable

@Immutable public class LongestCommonSubsequence extends Object implements StringDistance
The longest common subsequence (LCS) problem consists in finding the longest subsequence common to two (or more) sequences. It differs from problems of finding common substrings: unlike substrings, subsequences are not required to occupy consecutive positions within the original sequences. It is used by the diff utility, by Git for reconciling multiple changes, etc. The LCS distance between Strings X (length n) and Y (length m) is n + m - 2 |LCS(X, Y)| min = 0 max = n + m LCS distance is equivalent to Levenshtein distance, when only insertion and deletion is allowed (no substitution), or when the cost of the substitution is the double of the cost of an insertion or deletion. ! This class currently implements the dynamic programming approach, which has a space requirement O(m * n)!
See Also:
  • Constructor Details

    • LongestCommonSubsequence

      public LongestCommonSubsequence()
  • Method Details

    • distance

      public final double distance(String s1, String s2)
      Return the LCS distance between strings s1 and s2, computed as |s1| + |s2| - 2 * |LCS(s1, s2)|.
      Specified by:
      distance in interface StringDistance
      Parameters:
      s1 - The first string to compare.
      s2 - The second string to compare.
      Returns:
      the LCS distance between strings s1 and s2, computed as |s1| + |s2| - 2 * |LCS(s1, s2)|
      Throws:
      NullPointerException - if s1 or s2 is null.
    • length

      public final int length(String s1, String s2)
      Return the length of Longest Common Subsequence (LCS) between strings s1 and s2.
      Parameters:
      s1 - The first string to compare.
      s2 - The second string to compare.
      Returns:
      the length of LCS(s1, s2)
      Throws:
      NullPointerException - if s1 or s2 is null.