# 2360. Longest Cycle in a Graph

###### tags: `leetcode`,`memo`,`hard`

>ref: https://leetcode.com/problems/longest-cycle-in-a-graph/
>



>1. tc O(n) visit at most once
>2. sc O(n) record the visit timetag

class Solution {
    public int longestCycle(int[] edges) {

        //  use visit and increaing time as the length
        

        int[] visitT=new int[edges.length];
        // int time=1;

        int ans=-1;
        int time=1;

        for(int i=0;i<edges.length;i++){
            if(visitT[i]==0){
                int next= i;
                int st=time;

                while(next!=-1 && visitT[next]==0){
                    visitT[next]=time++;
                    next=edges[next];
                }
                if( next!=-1 && visitT[next]>=st){
                    ans=Math.max(ans,time-visitT[next]); // time cur not used, for next loop is ok
                }
            }
            
        }

        return ans;
    }
}