1923 - Longest Common Subpath.

Hard

There is a country of n cities numbered from 0 to n - 1. In this country, there is a road connecting every pair of cities.

There are m friends numbered from 0 to m - 1 who are traveling through the country. Each one of them will take a path consisting of some cities. Each path is represented by an integer array that contains the visited cities in order. The path may contain a city more than once , but the same city will not be listed consecutively.

Given an integer n and a 2D integer array paths where paths[i] is an integer array representing the path of the <code>i^th</code> friend, return the length of the longest common subpath that is shared by every friend's path, or 0 if there is no common subpath at all.

A subpath of a path is a contiguous sequence of cities within that path.

Example 1:

Input: n = 5, paths = \[\[0,1,2,3,4], 2,3,4, 4,0,1,2,3]

Output: 2

Explanation: The longest common subpath is 2,3.

Example 2:

Input: n = 3, paths = \[\[0],1,2]

Output: 0

Explanation: There is no common subpath shared by the three paths.

Example 3:

Input: n = 5, paths = \[\[0,1,2,3,4], 4,3,2,1,0]

Output: 1

Explanation: The possible longest common subpaths are 0, 1, 2, 3, and 4. All have a length of 1.

Constraints:

• <code>1 <= n <= 10⁵</code>

• m == paths.length

• <code>2 <= m <= 10⁵</code>

• <code>sum(pathsi.length) <= 10⁵</code>

• 0 <= paths[i][j] < n

• The same city is not listed multiple times consecutively in paths[i].