package DynamicProgramming;⏎
⏎
class LongestCommonSubsequence {⏎
⏎
    public static String getLCS(String str1, String str2) {⏎
⏎
        //At least one string is null⏎
        if (str1 == null || str2 == null)⏎
            return null;⏎
⏎
        //At least one string is empty⏎
        if (str1.length() == 0 || str2.length() == 0)⏎
            return "";⏎
⏎
        String[] arr1 = str1.split("");⏎
        String[] arr2 = str2.split("");⏎
⏎
        //lcsMatrix[i][j]  = LCS of first i elements of arr1 and first j characters of arr2⏎
        int[][] lcsMatrix = new int[arr1.length + 1][arr2.length + 1];⏎
⏎
        for (int i = 0; i < arr1.length + 1; i++)⏎
            lcsMatrix[i][0] = 0;⏎
        for (int j = 1; j < arr2.length + 1; j++)⏎
            lcsMatrix[0][j] = 0;⏎
        for (int i = 1; i < arr1.length + 1; i++) {⏎
            for (int j = 1; j < arr2.length + 1; j++) {⏎
                if (arr1[i - 1].equals(arr2[j - 1])) {⏎
                    lcsMatrix[i][j] = lcsMatrix[i - 1][j - 1] + 1;⏎
                } else {⏎
                    lcsMatrix[i][j] = lcsMatrix[i - 1][j] > lcsMatrix[i][j - 1] ? lcsMatrix[i - 1][j] : lcsMatrix[i][j - 1];⏎
                }⏎
            }⏎
        }⏎
        return lcsString(str1, str2, lcsMatrix);⏎
    }⏎
⏎
    public static String lcsString(String str1, String str2, int[][] lcsMatrix) {⏎
        StringBuilder lcs = new StringBuilder();⏎
        int i = str1.length(),⏎
                j = str2.length();⏎
        while (i > 0 && j > 0) {⏎
            if (str1.charAt(i - 1) == str2.charAt(j - 1)) {⏎
                lcs.append(str1.charAt(i - 1));⏎
                i--;⏎
                j--;⏎
            } else if (lcsMatrix[i - 1][j] > lcsMatrix[i][j - 1]) {⏎
                i--;⏎
            } else {⏎
                j--;⏎
            }⏎
        }⏎
        return lcs.reverse().toString();⏎
    }⏎
⏎
    public static void main(String[] args) {⏎
        String str1 = "DSGSHSRGSRHTRD";⏎
        String str2 = "DATRGAGTSHS";⏎
        String lcs = getLCS(str1, str2);⏎
⏎
        //Print LCS⏎
        if (lcs != null) {⏎
            System.out.println("String 1: " + str1);⏎
            System.out.println("String 2: " + str2);⏎
            System.out.println("LCS: " + lcs);⏎
            System.out.println("LCS length: " + lcs.length());⏎
        }⏎
    }⏎
⏎