Create 01 - DFS Approach.cpp

Author: JawadSher

23 - Graph Data Structure Problems/08 - Cycle Detection in Directed Graphs/01 - DFS Approach.cpp

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+class Solution {
+  public:
+    bool isDFSCycle(int node, vector<vector<int>>& adj, unordered_map<int, bool>& visited, unordered_map<int, bool>& dfsVisited){
+        visited[node] = true;
+        dfsVisited[node] = true;
+        
+        for(auto neighbour : adj[node]){
+            if(!visited[neighbour]){
+                bool cycleDetected = isDFSCycle(neighbour, adj, visited, dfsVisited);
+                if(cycleDetected) return true;
+            }else if(dfsVisited[neighbour]) return true;
+        }
+        
+        dfsVisited[node] = false;
+        return false;
+    }
+    
+    bool isCyclic(int V, vector<vector<int>> adj) {
+        unordered_map<int, bool> visited;
+        unordered_map<int, bool> dfsVisited;
+        
+        for(int i = 0; i < V; i++){
+            if(!visited[i]){
+                bool ans = isDFSCycle(i, adj, visited, dfsVisited);
+                if(ans == true) return true;
+            }
+        }
+        
+        return false;
+    }
+};