<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:

    int ans=-1;

    void dfs(vector<int> adj[],int s,int n,vector<bool> &visited,int l,vector<int> &depth,vector<bool> &recstack)
    {
        visited[s]=true;
        recstack[s]=true;
        depth[s]=l;
        for(auto x:adj[s])
        {
            if(visited[x]==false) dfs(adj,x,n,visited,l+1,depth,recstack);
            else 
            {
                if(recstack[x]==true) {ans=max(ans,abs(depth[x]-depth[s]));
                cout<<x<<' '<<s<<'\n';}
            }
        }
        recstack[s]=false;
    }

    int longestCycle(vector<int>& edges) {
        ios::sync_with_stdio(0);
        cin.tie(0);
        int E=edges.size();
        vector<int> adj[E];
        for(int i=0;i<E;i++)
        {
            if(edges[i]!=-1) adj[i].push_back(edges[i]);
        }
        vector<bool> visited(E);
        vector<bool> recstack(E);
        vector<int> depth(E);
        for(int i=0;i<E;i++)
        {
            if(visited[i]==false)
            {
                dfs(adj,i,E,visited,0,depth,recstack);
            }
        }
        if(ans==-1) return -1;
        else return ans+1;
    }
};
183525