1923. Longest Common Subpath

https://leetcode.com/problems/longest-common-subpath

Description

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 ith 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:

• 1 <= n <= 105

• m == paths.length

• 2 <= m <= 105

• sum(paths[i].length) <= 105

• 0 <= paths[i][j] < n

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

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