Create detect cycle in dfs

detect cycle in dfs

@@ -0,0 +1,60 @@
+import java.util.ArrayList;
+import java.util.List;
+
+public class Graph {
+    private final int V;
+    private final List<List<Integer>> adj;
+
+    public Graph(int V) {
+        this.V = V;
+        adj = new ArrayList<>(V);
+        for (int i = 0; i < V; i++) {
+            adj.add(new ArrayList<>());
+        }
+    }
+
+    public void addEdge(int v, int w) {
+        adj.get(v).add(w);
+        adj.get(w).add(v); // Since the graph is undirected
+    }
+
+    private boolean isCyclicUtil(int v, boolean[] visited, int parent) {
+        visited[v] = true;
+        for (Integer i : adj.get(v)) {
+            if (!visited[i]) {
+                if (isCyclicUtil(i, visited, v)) {
+                    return true;
+                }
+            } else if (i != parent) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    public boolean isCyclic() {
+        boolean[] visited = new boolean[V];
+        for (int i = 0; i < V; i++) {
+            if (!visited[i]) {
+                if (isCyclicUtil(i, visited, -1)) {
+                    return true;
+                }
+            }
+        }
+        return false;
+    }
+
+    public static void main(String[] args) {
+        Graph g = new Graph(4);
+        g.addEdge(0, 1);
+        g.addEdge(1, 2);
+        g.addEdge(2, 3);
+        g.addEdge(3, 0);
+
+        if (g.isCyclic()) {
+            System.out.println("Cycle detected");
+        } else {
+            System.out.println("No cycle detected");
+        }
+    }
+}