(UVA) Longest Common Subsequence - Solution

Link to the problem: https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=751&page=show_problem&problem=1346

The solution below used the concept of Longest Common Subsequence, related to Dynamic Programming, to solve this problem.


import java.io.*;
import java.util.*;

class Main {
    public String s1;
    public String s2;
    public int[][] memo;
   
    public int rec(int indexS1, int indexS2) {
        if (indexS1 == s1.length() || indexS2 == s2.length()) {
            return 0;
        }

        if (memo[indexS1][indexS2] != -1) {
            return memo[indexS1][indexS2];
        }
               
        int nextS1 = rec(indexS1+1, indexS2);
        int nextS2 = rec(indexS1, indexS2+1);
        int nextS1S2 = rec(indexS1+1, indexS2+1) + ((s1.charAt(indexS1) == s2.charAt(indexS2)) ? 1 : 0);
       
        memo[indexS1][indexS2] = Math.max(nextS1, Math.max(nextS2, nextS1S2));
        return memo[indexS1][indexS2];
    }
   
    public void process() throws NumberFormatException, IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));

        String line = br.readLine();
        while (line != null) {
            s1 = line;
            s2 = br.readLine();
           
            memo = new int[s1.length()][s2.length()];
            for (int i = 0; i < s1.length(); i++) {
                for (int j = 0; j < s2.length(); j++) {
                    memo[i][j] = -1;
                }
            }
           
            bw.write(rec(0, 0)+"\n");
           
            line = br.readLine();
        }
                                              
        bw.flush();
        bw.close();
       
        return;
    }
   
    public static void main(String[] args) throws NumberFormatException, IOException {
        Main m = new Main();
        m.process();
       
        System.exit(0);
    }
}