<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 memoi(self,s1,s2,m,n,dp):
        if n<0 or m<0:
            return 0
        if dp[m][n]!=-1:
            return dp[m][n]
        else:
            if s1[m]==s2[n]:
                dp[m][n]=1+self.memoi(s1,s2,m-1,n-1,dp)
                return dp[m][n]
            dp[m][n]=max(self.memoi(s1,s2,m-1,n,dp),self.memoi(s1,s2,m,n-1,dp))
            return dp[m][n]
    def tabulation(self,s1,s2,m):
        tab=[[0 for i in range(m)]for j in range(m)]
        for i in range(m):
            if s1[0] in s2[:i+1]:
                tab[0][i]=1
            if s2[0] in s1[:i+1]:
                tab[i][0]=1
        for i in range(1,m):
            for j in range(1,m):
                if s1[i]==s2[j]:
                    tab[i][j]=1+tab[i-1][j-1]
                else:
                    tab[i][j]=max(tab[i-1][j],tab[i][j-1])
        return tab[m-1][m-1]
            
    def longestPalindromeSubseq(self, s: str) -> int:
        m=len(s)
        dp=[[-1 for i in range(m)]for j in range(m)]
        # ans_m=self.memoi(s,s[::-1],m-1,m-1,dp)
        ans_t=self.tabulation(s,s[::-1],m)
        return ans_t
        
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