Given a string s, find the longest substring that appears at least twice in s and return its length. The two occurrences may overlap. If no such substring exists, return 0.

Example 1:

Input: "agefdefag"
Output: 2
Explanation: The substrings "ag" and "ef" each appear twice in the string. Both have a length of 2, which is the longest among all repeating substrings.

Example 2:

Input: "abcdefg"
Output: 0
Explanation: No repeating substrings exist.

Example 3:

Input: "aaaaa"
Output: 4
Explanation: The substrings "aaaa", "aaa", etc., repeat. The longest is "aaaa" (repeats starting at index 0 and 1).

| --------- | --------------- | -------------------------------- |
| Substring | Start Positions | Repeats?                         |
| --------- | --------------- | -------------------------------- |
|  "a"      | 0, 1, 2, 3, 4   | ✅ Yes (many times)              |
| --------- | --------------- | -------------------------------- |
|  "aa"     | 0, 1, 2, 3      | ✅ Yes                           |
| --------- | --------------- | -------------------------------- |
|  "aaa"    | 0, 1, 2         | ✅ Yes                           |
| --------- | --------------- | -------------------------------- |
|  "aaaa"   | 0, 1            | ✅ Yes                           |
| --------- | --------------- | -------------------------------- |
|  "aaaaa"  | 0 only          | ❌ No (full string can't repeat) |
| --------- | --------------- | -------------------------------- |

Example 4:

Input: "hasabckhabcha"
Output: 3
Explanation: 
The substring "abc" is the longest repeating substring, appearing at indices 3 and 8. Its length is 3.
The string positions are:
Index 3: s[3...5] = "abc"
Index 8: s[8...10] = "abc"

Other repeating substrings:
"ha" appears at indices 0, 7, and 11, but its length is only 2
"ab" also repeats more than once, but is shorter (length = 2)

Constraints

1 <= s.length <= 2000

s consists of lowercase English letters.

93. Longest Repeated Substring