Added Tortoise and Hare algorithm with unit tests

Author: Chintha-vardhan

src/main/java/com/thealgorithms/LinkedList/DoublyLinkedLIst.java

@@ -0,0 +1,30 @@
+package com.thealgorithms.LinkedList;
+
+/**
+ * Detects a cycle in a singly linked list using Tortoise and Hare algorithm
+ */
+public class TortoiseAndHare {
+
+    static class ListNode {
+        int val;
+        ListNode next;
+
+        ListNode(int x) {
+            this.val = x;
+            next = null;
+        }
+    }
+
+    public boolean hasCycle(ListNode head) {
+        ListNode slow = head;
+        ListNode fast = head;
+
+        while (fast != null && fast.next != null) {
+            slow = slow.next;
+            fast = fast.next.next;
+
+            if (slow == fast) return true;
+        }
+        return false;
+    }
+}