Merge pull request #281 from Shivam20233/master

Added Floyd’s Cycle-Finding Algorithm

Author: master-fury

Data_Structure/src/Linked Lists/Floyd’s Cycle-Finding Algorithm

@@ -0,0 +1,65 @@
+// This algorithm is used to find a loop in a linked list. It uses two pointers one moving twice 
+// as fast as the other one. The faster one is called the faster pointer and the other one is 
+// called the slow pointer.
+
+#include <bits/stdc++.h>
+using namespace std;
+
+/* Link list node */
+class Node {
+public:
+	int data;
+	Node* next;
+};
+
+void push(Node** head_ref, int new_data)
+{
+	/* allocate node */
+	Node* new_node = new Node();
+
+	/* put in the data */
+	new_node->data = new_data;
+
+	/* link the old list off the new node */
+	new_node->next = (*head_ref);
+
+	/* move the head to point to the new node */
+	(*head_ref) = new_node;
+}
+
+int detectLoop(Node* list)
+{
+	Node *slow_p = list, *fast_p = list;
+
+	while (slow_p && fast_p && fast_p->next) {
+		slow_p = slow_p->next;
+		fast_p = fast_p->next->next;
+		if (slow_p == fast_p) {
+			return 1;
+		}
+	}
+	return 0;
+}
+
+/* Driver code*/
+int main()
+{
+	/* Start with the empty list */
+	Node* head = NULL;
+
+	push(&head, 20);
+	push(&head, 4);
+	push(&head, 15);
+	push(&head, 10);
+
+	/* Create a loop for testing */
+	head->next->next->next->next = head;
+	if (detectLoop(head))
+		cout << "Loop Found";
+	else
+		cout << "No Loop";
+	return 0;
+}
+
+Time complexity: O(N).
+Auxiliary Space: O(1).