{ "data": { "question": { "questionId": "2439", "questionFrontendId": "2360", "categoryTitle": "Algorithms", "boundTopicId": 1706855, "title": "Longest Cycle in a Graph", "titleSlug": "longest-cycle-in-a-graph", "content": "

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

\n\n

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.

\n\n

Return the length of the longest cycle in the graph. If no cycle exists, return -1.

\n\n

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

\n\n

 

\n

Example 1:

\n\"\"\n
\nInput: edges = [3,3,4,2,3]\nOutput: 3\nExplanation: The longest cycle in the graph is the cycle: 2 -> 4 -> 3 -> 2.\nThe length of this cycle is 3, so 3 is returned.\n
\n\n

Example 2:

\n\"\"\n
\nInput: edges = [2,-1,3,1]\nOutput: -1\nExplanation: There are no cycles in this graph.\n
\n\n

 

\n

Constraints:

\n\n\n", "translatedTitle": "图中的最长环", "translatedContent": "

给你一个 n 个节点的 有向图 ,节点编号为 0 到 n - 1 ,其中每个节点 至多 有一条出边。

\n\n

图用一个大小为 n 下标从 0 开始的数组 edges 表示,节点 i 到节点 edges[i] 之间有一条有向边。如果节点 i 没有出边,那么 edges[i] == -1 。

\n\n

请你返回图中的 最长 环,如果没有任何环,请返回 -1 。

\n\n

一个环指的是起点和终点是 同一个 节点的路径。

\n\n

 

\n\n

示例 1:

\n\n

\"\"

\n\n
\n输入:edges = [3,3,4,2,3]\n输出去:3\n解释:图中的最长环是:2 -> 4 -> 3 -> 2 。\n这个环的长度为 3 ,所以返回 3 。\n
\n\n

示例 2:

\n\n

\"\"

\n\n
\n输入:edges = [2,-1,3,1]\n输出:-1\n解释:图中没有任何环。\n
\n\n

 

\n\n

提示:

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