DataStructure-And-Algorithms/Graph Theory/GraphIntro14.cpp at master · anagh9/DataStructure-And-Algorithms · GitHub

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//Cycle Detection in directed Graph

#include <bits/stdc++.h>
using namespace std;


// } Driver Code Ends
/*  Function to check if the given graph contains cycle
*   V: number of vertices
*   adj[]: representation of graph
*/
bool isCyclic_util(vector<int> adj[], vector<bool> visited, int curr)
{
  if (visited[curr] == true)
    return true;

  visited[curr] = true;
  bool FLAG = false;
  for (int i = 0; i < adj[curr].size(); ++i)
  {
    FLAG = isCyclic_util(adj, visited, adj[curr][i]);
    if (FLAG == true)
      return true;
  }
  return false;
}

bool isCyclic(int V, vector<int> adj[])
{
  vector<bool> visited(V, false);
  bool FLAG = false;
  for (int i = 0; i < V; ++i)
  {
    visited[i] = true;
    for (int j = 0; j < adj[i].size(); ++j)
    {
      FLAG = isCyclic_util(adj, visited, adj[i][j]);
      if (FLAG == true)
        return true;
    }
    visited[i] = false;
  }
  return false;
}

// { Driver Code Starts.

int main() {

  int t;
  cin >> t;

  while (t--) {

    int v, e;
    cin >> v >> e;

    vector<int> adj[v];

    for (int i = 0; i < e; i++) {
      int u, v;
      cin >> u >> v;
      adj[u].push_back(v);
    }

    cout << isCyclic(v, adj) << endl;

  }

  return 0;
}  // } Driver Code Ends