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# 1044. Longest Duplicate Substring

<https://leetcode.com/problems/longest-duplicate-substring>

## Description

Given a string `s`, consider all *duplicated substrings*: (contiguous) substrings of s that occur 2 or more times. The occurrences may overlap.

Return **any** duplicated substring that has the longest possible length. If `s` does not have a duplicated substring, the answer is `""`.

**Example 1:**

```
**Input:** s = "banana"
**Output:** "ana"
```

**Example 2:**

```
**Input:** s = "abcd"
**Output:** ""
```

**Constraints:**

* `2 <= s.length <= 3 * 104`
* `s` consists of lowercase English letters.

## ac

```java
```