Cycle Detection

Author: jaisat

Graph/detectCycle.cpp

@@ -0,0 +1,62 @@
+#include<bits/stdc++.h>
+using namespace std;
+class Graph {
+
+	int  v;
+	list<int> *l;
+public:
+	Graph(int v) {
+		this->v = v;
+		l = new list<int>[v];
+	}
+	void addEdge(int x, int y) {
+		l[x].push_back(y);
+	}
+
+	bool cycle_helper(int src, bool *visited, bool *stack) {
+		visited[src] = true;
+		stack[src] = true;
+
+		for (auto nbr : l[src]) {
+			if (stack[nbr] == true) {
+				return true;
+			} else if (!visited[nbr]) {
+				bool found = cycle_helper(nbr, visited, stack);
+				if (found) {
+					return true;
+				}
+			}
+		}
+		stack[src] = false;
+		return false;
+	}
+	bool dfs() {
+		bool *visited = new bool[v];
+		bool *stack = new bool[v];
+
+		for (int i = 0; i < v; i++) {
+			visited[i] = stack[i] = false;
+		}
+
+		return cycle_helper(0, visited, stack);
+	}
+};
+int main() {
+
+	Graph g(7);
+	g.addEdge(0, 1);
+	g.addEdge(1, 2);
+	g.addEdge(2, 3);
+	g.addEdge(3, 4);
+	g.addEdge(4, 5);
+	g.addEdge(1, 5);
+	g.addEdge(5, 6);
+	//g.addEdge(4,2);
+
+	if (g.dfs()) {
+		cout << "Yes" << endl;
+	} else {
+		cout << "No" << endl;
+	}
+	return 0;
+}