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

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

<p>Return <em>the length of the <strong>longest</strong> cycle in the graph</em>. If no cycle exists, return <code>-1</code>.</p>

<p>A cycle is a path that starts and ends at the <strong>same</strong> node.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2022/06/08/graph4drawio-5.png" style="width: 335px; height: 191px;" />
<pre>
<strong>Input:</strong> edges = [3,3,4,2,3]
<strong>Output:</strong> 3
<strong>Explanation:</strong> The longest cycle in the graph is the cycle: 2 -&gt; 4 -&gt; 3 -&gt; 2.
The length of this cycle is 3, so 3 is returned.
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2022/06/07/graph4drawio-1.png" style="width: 171px; height: 161px;" />
<pre>
<strong>Input:</strong> edges = [2,-1,3,1]
<strong>Output:</strong> -1
<strong>Explanation:</strong> There are no cycles in this graph.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>n == edges.length</code></li>
	<li><code>2 &lt;= n &lt;= 10<sup>5</sup></code></li>
	<li><code>-1 &lt;= edges[i] &lt; n</code></li>
	<li><code>edges[i] != i</code></li>
</ul>

class Solution {
public:
    bool dfs(int i,vector<int>&cnt,vector<int>&visited,vector<int>&path,vector<int>adj[])
    {
        visited[i]=1;
        path[i]=1;
        cnt.push_back(i);
        for(auto it:adj[i])
        {
            if(!visited[it])
            {
                if(dfs(it,cnt,visited,path,adj))
                 return true;
            }
            else if(path[it]) 
            {
                cnt.push_back(it);
                return true;
            }
        }
        
        cnt.pop_back();
        path[i]=0;
        return false;
    }
    int longestCycle(vector<int>& edges) {
        int n=edges.size();

        vector<int>adj[n];
        for(int i=0;i<n;i++) if(edges[i]>=0) adj[i].push_back(edges[i]);

        vector<int>visited(n),path(n);
        int ans=INT_MIN;

        for(int i=0;i<n;i++)
        {
            if(!visited[i])
            {
                vector<int>cnt;
                if(dfs(i,cnt,visited,path,adj))
                {
                    int temp=cnt.back(),j=0;
                    for(j;j<cnt.size();j++) if(cnt[j]==temp) break;
                    int val=cnt.size()-j-1;
                    ans=max(ans,val);
                }
            }
        }
        if(ans==INT_MIN) return -1;
        return ans;
    }
};
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