Android String Levenshtein Distance Get computeLevenshteinDistance(CharSequence str1, CharSequence str2)

Description

compute Levenshtein Distance

Declaration

public static int computeLevenshteinDistance(CharSequence str1,
            CharSequence str2) 

Method Source Code

//package com.java2s;

public class Main {
    public static int computeLevenshteinDistance(CharSequence str1,
            CharSequence str2) {//from  w ww.j  av  a  2s  .  c om

        int commonPrefixLength = findCommonPrefixLength(str1, str2);

        if (commonPrefixLength == str1.length()
                && commonPrefixLength == str2.length()) {
            return 0; // same exact string
        }

        int commonSuffixLength = findCommonSuffixLength(str1, str2,
                commonPrefixLength);

        str1 = str1.subSequence(commonPrefixLength, str1.length()
                - commonSuffixLength);
        str2 = str2.subSequence(commonPrefixLength, str2.length()
                - commonSuffixLength);

        int[][] distance = new int[str1.length() + 1][str2.length() + 1];

        for (int i = 0; i <= str1.length(); i++) {
            distance[i][0] = i;
        }
        for (int j = 0; j <= str2.length(); j++) {
            distance[0][j] = j;
        }

        for (int i = 1; i <= str1.length(); i++) {
            for (int j = 1; j <= str2.length(); j++) {
                distance[i][j] = minimum(
                        distance[i - 1][j] + 1,
                        distance[i][j - 1] + 1,
                        distance[i - 1][j - 1]
                                + ((str1.charAt(i - 1) == str2
                                        .charAt(j - 1)) ? 0 : 1));
            }
        }

        int dist = distance[str1.length()][str2.length()];

        return dist;
    }

    private static int findCommonPrefixLength(CharSequence str1,
            CharSequence str2) {

        int length = (Math.min(str1.length(), str2.length()));
        for (int i = 0; i < length; i++) {
            if (str1.charAt(i) != str2.charAt(i)) {
                return i;
            }
        }

        return 0;

    }

    private static int findCommonSuffixLength(CharSequence str1,
            CharSequence str2, int commonPrefixLength) {
        int length = (Math.min(str1.length(), str2.length()));
        for (int i = 0; i < length - commonPrefixLength; i++) {
            if (str1.charAt(str1.length() - i - 1) != str2.charAt(str2
                    .length() - i - 1)) {
                return i;
            }
        }

        return 0;
    }

    private static int minimum(int a, int b, int c) {
        return Math.min(Math.min(a, b), c);
    }
}