2360\. Longest Cycle in a Graph

Hard

You are given a **directed** graph of `n` nodes numbered from `0` to `n - 1`, where each node has **at most one** outgoing edge.

The graph is represented with a given **0-indexed** array `edges` of size `n`, indicating that there is a directed edge from node `i` to node `edges[i]`. If there is no outgoing edge from node `i`, then `edges[i] == -1`.

Return _the length of the **longest** cycle in the graph_. If no cycle exists, return `-1`.

A cycle is a path that starts and ends at the **same** node.

**Example 1:**

![](https://assets.leetcode.com/uploads/2022/06/08/graph4drawio-5.png)

**Input:** edges = [3,3,4,2,3]

**Output:** 3

**Explanation:** The longest cycle in the graph is the cycle: 2 -> 4 -> 3 -> 2.

The length of this cycle is 3, so 3 is returned. 

**Example 2:**

![](https://assets.leetcode.com/uploads/2022/06/07/graph4drawio-1.png)

**Input:** edges = [2,-1,3,1]

**Output:** -1

**Explanation:** There are no cycles in this graph. 

**Constraints:**

*   `n == edges.length`
*   <code>2 <= n <= 10<sup>5</sup></code>
*   `-1 <= edges[i] < n`
*   `edges[i] != i`