<p>Given a string <code>s</code>, partition <code>s</code> such that every <span data-keyword="substring-nonempty">substring</span> of the partition is a <span data-keyword="palindrome-string"><strong>palindrome</strong></span>. Return <em>all possible palindrome partitioning of </em><code>s</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<pre><strong>Input:</strong> s = "aab"
<strong>Output:</strong> [["a","a","b"],["aa","b"]]
</pre><p><strong class="example">Example 2:</strong></p>
<pre><strong>Input:</strong> s = "a"
<strong>Output:</strong> [["a"]]
</pre>
<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= s.length &lt;= 16</code></li>
	<li><code>s</code> contains only lowercase English letters.</li>
</ul>

class Solution:
    def rec(self, i, last, substr):
        if i == -1:
            sum_length = 0
            for s in substr:
                sum_length += len(s)
                if s != s[::-1]:
                    break
            else:
                if sum_length == len(self.s):
                    self.ans.append(substr[::-1])
            return

        self.rec(i - 1, last, substr)
        self.rec(i - 1, i, substr + [self.s[i:last]])

    def partition(self, s: str) -> List[List[str]]:
        self.ans = []
        self.s = s
        self.rec(len(s) - 1, len(s), [])
        return self.ans
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