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 C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include<bits/stdc++.h>
using namespace std;
int main()
{
	string s1,s2;
	cin>>s1>>s2;
	int n = s1.length();
	int m = s2.length();
	int dp[n+1][m+1];
	for(int i=0;i<=n;i++)
	{
		for(int j=0;j<=m;j++)
		{
			if(i==0 || j==0)
			{
				dp[i][j] = 0;
			}
			else if(s1[i-1] == s2[j-1])
			{
				dp[i][j] = dp[i-1][j-1] + 1;
			}
			else
			{
				dp[i][j] = max(dp[i-1][j],dp[i][j-1]);
			}
		}
	}
	string res = "";
	int ind = dp[n][m];
	int i=n,j=m;
	while(i>0 && j>0)
	{
		if(s1[i-1] == s2[j-1])
		{
			res += s1[i-1];
			i--;
			j--;
			ind--;
		}
		else if(dp[i-1][j]>dp[i][j-1])
		{
			i--;
		}
		else
		{
			j--;
		}
	}
	reverse(res.begin(),res.end());
	if(res.size()==0)
	{
		cout<<" ";
		return 0;
	}
	cout<<res<<"\n";
	return 0;
}