{ "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.
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.
\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\nn == edges.length
2 <= n <= 105
-1 <= edges[i] < n
edges[i] != i
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。
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
。
请你返回图中的 最长 环,如果没有任何环,请返回 -1
。
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:
\n\nn == edges.length
2 <= n <= 105
-1 <= edges[i] < n
edges[i] != i
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