<p>Given a string <code>s</code>, find <em>the longest palindromic <strong>subsequence</strong>&#39;s length in</em> <code>s</code>.</p>

<p>A <strong>subsequence</strong> is a sequence that can be derived from another sequence by deleting some or no elements without changing the order of the remaining elements.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;bbbab&quot;
<strong>Output:</strong> 4
<strong>Explanation:</strong> One possible longest palindromic subsequence is &quot;bbbb&quot;.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;cbbd&quot;
<strong>Output:</strong> 2
<strong>Explanation:</strong> One possible longest palindromic subsequence is &quot;bb&quot;.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= s.length &lt;= 1000</code></li>
	<li><code>s</code> consists only of lowercase English letters.</li>
</ul>

class Solution:
    def longestPalindromeSubseq(self, s: str) -> int:
        n = len(s)
        cache = [[-1] * n for i in range(n)]
        return self.helper(s, 0, n - 1, cache)

    def helper(self, s: str, i: int, j: int, cache: list) -> int:
        if i > j:
            return 0

        if i == j:
            return 1

        if cache[i][j] == -1:
            if s[i] == s[j]:
                cache[i][j] = self.helper(s, i + 1, j - 1, cache) + 2
            else:
                left = self.helper(s, i + 1, j, cache)
                right = self.helper(s, i, j - 1, cache)
                cache[i][j] = max(left, right)

        return cache[i][j]

        
28668