LeetCode 516 Longest Palindromic Subsequence - Walkthrough

Find the longest palindromic subsequence in $s$. observation: LPS$(s)$ = LCS$(s, reverse(s))$. Why? A palindrome reads the same forwards and backwards.

So the common subsequence between $s$ and its reverse is palindromic. Example: $s = \text{"bbbab"}$. Reverse: "babbb". LCS = "bbbb" with length $4$. Alternative: direct DP with $dp[i][j]$ = LPS of $s[i..j]$. Transition: if $s[i] = s[j]$, extend; else take max of excluding either end.