info.debatty.java.stringsimilarity

Class LongestCommonSubsequence

java.lang.Object

info.debatty.java.stringsimilarity.LongestCommonSubsequence

All Implemented Interfaces:

StringSimilarityInterface

public class LongestCommonSubsequence
extends Object
implements StringSimilarityInterface

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)!

Author:

tibo

Constructor Summary

Constructors

Constructor and Description
LongestCommonSubsequence()

Method Summary

Methods

Modifier and Type	Method and Description
double	distance(String s1, String s2) Generally, distance = 1 - similarity.
static int	Distance(String s1, String s2)
int	distanceAbsolute(String s1, String s2)
int	length(String s1, String s2)
static void	main(String[] args)
double	similarity(String s1, String s2)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

LongestCommonSubsequence

public LongestCommonSubsequence()

Method Detail

main

public static void main(String[] args)

Parameters:

args - the command line arguments

Distance

public static int Distance(String s1,
           String s2)

similarity

public double similarity(String s1,
                String s2)

Specified by:

similarity in interface StringSimilarityInterface

Returns:

similarity between 0 (completely different) and 1 (s1 = s2)

distance

public double distance(String s1,
              String s2)

Description copied from interface: StringSimilarityInterface

Generally, distance = 1 - similarity. Some implementations can also provide a method distanceAbsolute

Specified by:

distance in interface StringSimilarityInterface

Returns:

distance between 0 (s1 = s2) and 1 (completely different)

distanceAbsolute

public int distanceAbsolute(String s1,
                   String s2)

length

public int length(String s1,
         String s2)