Java LCS lcse(String str1, String str2)

Description

lcse

License

Open Source License

Declaration

public static String lcse(String str1, String str2) 

Method Source Code

//package com.java2s;
//License from project: Open Source License 

public class Main {
    public static String lcse(String str1, String str2) {

        if (null == str1 || null == str2 || str1.equals("") || str2.equals("")) {
            return "";
        }/*from   w  ww .  j  ava  2 s  .  co m*/

        char[] chs1 = str1.toCharArray();
        char[] chs2 = str2.toCharArray();

        int[][] dp = getDp(chs1, chs2);
        int m = chs1.length - 1;
        int n = chs2.length - 1;
        char[] res = new char[dp[m][n]];
        int index = res.length - 1;
        while (index >= 0) {
            if (n > 0 && dp[m][n] == dp[m][n - 1]) {
                n--;
            } else if (m > 0 && dp[m][n] == dp[m - 1][n]) {
                m--;
            } else {
                res[index--] = chs1[m];
                m--;
                n--;
            }
        }

        return String.valueOf(res);
    }

    private static int[][] getDp(char[] str1, char[] str2) {

        int[][] dp = new int[str1.length][str2.length];
        dp[0][0] = str1[0] == str2[0] ? 1 : 0;

        for (int i = 1; i < str1.length; i++) {
            dp[i][0] = Math.max(dp[i - 1][0], str1[i] == str2[0] ? 1 : 0);
        }

        for (int i = 1; i < str2.length; i++) {
            dp[0][i] = Math.max(dp[0][i - 1], str1[0] == str2[i] ? 1 : 0);
        }

        for (int i = 1; i < str1.length; i++) {
            for (int j = 1; j < str2.length; j++) {
                dp[i][j] = Math.max(dp[i - 1][j], dp[i][j - 1]);
                if (str1[i] == str2[j]) {
                    dp[i][j] = Math.max(dp[i][j], dp[i - 1][j - 1] + 1);
                }
            }
        }

        return dp;
    }
}

Related

1. lcs1(int[] A, int[] B)
2. lcs2(int[] A, int[] B, int m, int n)
3. lcs3(int[] A, int[] B)
4. lcs4(int[] A, int[] B)
5. LCSAlgorithm(String a, String b)
6. LCSIterative(Character[] X, int i, Character Y[], int j, int c[][])
7. LCSRecursive(Character[] X, int i, Character Y[], int j, int c[][])