Create 02 - DFS Approach.cpp

Author: JawadSher

23 - Graph Data Structure Problems/07 - Undirected Graph Cycle | BFS - DFS/02 - DFS Approach.cpp

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+class Solution {
+  public:
+    bool isCycleDFS(int node, int parent, unordered_map<int, bool> &visited, vector<vector<int>>& adj){
+        visited[node] = true;
+        
+        for(auto neighbour : adj[node]){
+            if(!visited[neighbour]){
+                bool cycleDetected = isCycleDFS(neighbour, node, visited, adj);
+                if(cycleDetected) return true;
+            }else if(neighbour != parent) return true;
+        }
+        
+        return false;
+    }
+    
+    bool isCycle(vector<vector<int>>& adj) {
+        int n = adj.size();
+        
+        unordered_map<int, bool> visited;
+        for(int i = 0; i < n; i++){
+            if(!visited[i]){
+                bool ans = isCycleDFS(i, -1, visited, adj);
+                if(ans == 1) return true;
+            }
+        }
+        
+        
+        return false;
+    }
+};