Longest Duplicate Substring
<p>Given a string <code>s</code>, consider all <em>duplicated substrings</em>: (contiguous) substrings of s that occur 2 or more times.&nbsp;The occurrences&nbsp;may overlap.</p>

<p>Return <strong>any</strong> duplicated&nbsp;substring that has the longest possible length.&nbsp;If <code>s</code> does not have a duplicated substring, the answer is <code>&quot;&quot;</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<pre><strong>Input:</strong> s = "banana"
<strong>Output:</strong> "ana"
</pre><p><strong class="example">Example 2:</strong></p>
<pre><strong>Input:</strong> s = "abcd"
<strong>Output:</strong> ""
</pre>
<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>2 &lt;= s.length &lt;= 3 * 10<sup>4</sup></code></li>
	<li><code>s</code> consists of lowercase English letters.</li>
</ul>
String; Binary Search; Suffix Array; Sliding Window; Hash Function; Rolling Hash
class Solution:
    def longestDupSubstring(self, s: str) -> str:
        def check(l):
            vis = set()
            for i in range(n - l + 1):
                t = s[i : i + l]
                if t in vis:
                    return t
                vis.add(t)
            return ''

        n = len(s)
        left, right = 0, n
        ans = ''
        while left < right:
            mid = (left + right + 1) >> 1
            t = check(mid)
            ans = t or ans
            if t:
                left = mid
            else:
                right = mid - 1
        return ans
