<p>There is a strange printer with the following two special properties:</p>

<ul>
	<li>The printer can only print a sequence of <strong>the same character</strong> each time.</li>
	<li>At each turn, the printer can print new characters starting from and ending at any place and will cover the original existing characters.</li>
</ul>

<p>Given a string <code>s</code>, return <em>the minimum number of turns the printer needed to print it</em>.</p>

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

<pre>
<strong>Input:</strong> s = &quot;aaabbb&quot;
<strong>Output:</strong> 2
<strong>Explanation:</strong> Print &quot;aaa&quot; first and then print &quot;bbb&quot;.
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;aba&quot;
<strong>Output:</strong> 2
<strong>Explanation:</strong> Print &quot;aaa&quot; first and then print &quot;b&quot; from the second place of the string, which will cover the existing character &#39;a&#39;.
</pre>

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

<ul>
	<li><code>1 &lt;= s.length &lt;= 100</code></li>
	<li><code>s</code> consists of lowercase English letters.</li>
</ul>

class Solution:
    def strangePrinter(self, s: str) -> int:
        a="".join(ch for ch, _ in itertools.groupby(s))
        n = len(a)
        h = {}
        t = [n] * n
        for i in reversed(range(n)):
            if a[i] in h:
                t[i] = h[a[i]]
            h[a[i]] = i
        d = [[0] * n for _ in range(n + 1)]
        for i in range(n):
            d[i][i] = 1
        for i in range(n - 2, -1, -1):
            for j in range(i + 1, n):
                d[i][j] = 1 + d[i + 1][j]
                k = t[i]
                while k <= j:
                    d[i][j] = min(d[i][j], d[i][k - 1] + d[k + 1][j])
                    k = t[k]
        return d[0][n - 1]
        
16700