<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 {
public:
    int solveUsingTabSO(string &a, string&b)
    {
        vector<int>next(a.size()+1,0);
        vector<int>curr(a.size()+1,0);
    
    for(int l = b.size()-1;l>=0;l--)
    {
        for(int k = a.size()-1;k>=0;k--)
        
        {
            int ans=0;
            if(a[k]==b[l])
            {
                ans = 1 + next[k+1];
            }
            else
            {
                ans = 0 + max(next[k],curr[k+1]);
            }

            curr[k]=ans;
        }
        next=curr;
    }
        return next[0];
    }
    int longestPalindromeSubseq(string s) {
        string a = s;
        reverse(a.begin(),a.end());
        int ans = solveUsingTabSO(s,a); // refer Longest common subsequnce leetcode question
        return ans;
    }
};
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