<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 longestPalindromeSubseq(string s) {
        int m = s.size();

        int tab[3][m];
        for (int i = 0; i < m; i++) {
            tab[0][i] = 0;
            tab[1][i] = 1;
        }
        int _2, _1, _0;
        for (int gap = 1; gap < m; gap++) {
            _2 = (gap + 1) % 3, _1 = (gap + 3) % 3, _0 = (gap - 1) % 3;
            for (int i = 0, j = gap; j < m; i++, j++) {
                if (s[i] == s[j]) {
                    tab[_2][j] = tab[_0][j - 1] + 2;
                } else {
                    tab[_2][j] = max(tab[_1][j], tab[_1][j - 1]);
                }
            }
        }
        return tab[m % 3][m - 1];
    }
};
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