Given a sequence, print a longest palindromic subsequence of it.
Input : BBABCBCAB Output : BABCBAB The above output is the longest palindromic subsequence of given sequence. "BBBBB" and "BBCBB" are also palindromic subsequences of the given sequence, but not the longest ones. Input : GEEKSFORGEEKS Output : Output can be either EEKEE or EESEE or EEGEE, ..
We have discussed a solution in below post to find length of longest palindromic subsequence.
Dynamic Programming | Set 12 (Longest Palindromic Subsequence)
In this post a solution to print the longest palindromic subsequence is discussed.
This problem is close to the Longest Common Subsequence (LCS) problem. In fact, we can use LCS as a subroutine to solve this problem. Following is the two step solution that uses LCS.
1) Reverse the given sequence and store the reverse in another array say rev[0..n-1]
2) LCS of the given sequence and rev will be the longest palindromic sequence.
3) Once we have found LCS, we can print the LCS.
Below is the implementation of above approach: