Problem:
Score : 100 points

Problem Statement

You are given strings s and t.
Find one longest string that is a subsequence of both s and t.

Notes

A subsequence of a string x is the string obtained by removing zero or more characters from x and concatenating the remaining characters without changing the order.

Constraints

s and t are strings consisting of lowercase English letters.

1 \leq |s|, |t| \leq 3000

Input

Input is given from Standard Input in the following format:

s
t

Output

Print one longest string that is a subsequence of both s and t.
If there are multiple such strings, any of them will be accepted.

Sample Input 1

axyb
abyxb

Sample Output 1

axb

The answer is axb or ayb; either will be accepted.

Sample Input 2

aa
xayaz

Sample Output 2

aa

Sample Input 3

a
z

Sample Output 3

The answer is (an empty string).

Sample Input 4

abracadabra
avadakedavra

Sample Output 4

aaadara

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Wrong Answer)

import java.util.*;

class Main {

    String s;
    String t;

    private void run() {

        Scanner sc = new Scanner(System.in);
        s = sc.next();
        t = sc.next();

        int S = s.length();
        int T = t.length();

        int[][] dp = new int[S+1][T+1];
        StringBuilder sb = new StringBuilder();

        for (int i = 0; i <= S; i++) {
            for (int j = 0; j <= T; j++) {
                if (i == 0 || j == 0) dp[i][j] = 0;
                else if (s.charAt(i-1) == t.charAt(j-1)) {
                    sb.append(s.charAt(i-1));
                    dp[i][j] = dp[i-1][j-1] + 1;
                } else if (dp[i-1][j] > dp[i][j-1]) {
                    dp[i][j] = dp[i-1][j];
                } else {
                    dp[i][j] = dp[i][j-1];
                }
            }
        }

        System.out.println(sb.substring(sb.length()/2));
    }


    public static void main(String[] args) {
        Main solver = new Main();
        solver.run();
    }
}