Create graph-cycle_detection.cpp

Algorithms/graph-cycle_detection.cpp

@@ -0,0 +1,96 @@
+
+#include <bits/stdc++.h>
+using namespace std;
+class Graph {
+
+
+    int V;
+    list<int>* adj;
+    bool isCyclicUtil(int v, bool visited[], int parent);
+
+public:
+
+    Graph(int V);
+
+
+    void addEdge(int v, int w);
+
+
+    bool isCyclic();
+};
+
+Graph::Graph(int V)
+{
+    this->V = V;
+    adj = new list<int>[V];
+}
+
+void Graph::addEdge(int v, int w)
+{
+
+   .
+    adj[v].push_back(w);
+
+
+    adj[w].push_back(v);
+}
+
+bool Graph::isCyclicUtil(int v, bool visited[], int parent)
+{
+
+
+    visited[v] = true;
+    list<int>::iterator i;
+    for (i = adj[v].begin(); i != adj[v].end(); ++i) {
+
+
+        if (!visited[*i]) {
+            if (isCyclicUtil(*i, visited, v))
+                return true;
+        }
+
+        else if (*i != parent)
+            return true;
+    }
+    return false;
+}
+
+bool Graph::isCyclic()
+{
+
+
+    bool* visited = new bool[V];
+    for (int i = 0; i < V; i++)
+        visited[i] = false;
+
+
+    for (int u = 0; u < V; u++) {
+
+
+        if (!visited[u])
+            if (isCyclicUtil(u, visited, -1))
+                return true;
+    }
+    return false;
+}
+
+
+int main()
+{
+    Graph g1(5);
+    g1.addEdge(1, 0);
+    g1.addEdge(0, 2);
+    g1.addEdge(2, 1);
+    g1.addEdge(0, 3);
+    g1.addEdge(3, 4);
+    g1.isCyclic() ? cout << "Graph contains cycle\n"
+                  : cout << "Graph doesn't contain cycle\n";
+
+    Graph g2(3);
+    g2.addEdge(0, 1);
+    g2.addEdge(1, 2);
+    g2.isCyclic() ? cout << "Graph contains cycle\n"
+                  : cout << "Graph doesn't contain cycle\n";
+
+    return 0;
+}