LinkedListDetectCycle Alogrithm

Author: melmedany

src/main/java/LinkedListsDetectCycle.java

@@ -0,0 +1,27 @@
+
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class LinkedListsDetectCycle {
+
+	public boolean solve(Node head) {
+		List<String> visited = new ArrayList<String>();
+		if (head == null) {
+			return false;
+		} else {
+			visited.add("@" + System.identityHashCode(head));
+			Node next = head.next;
+			while (next != null) {
+				int hash = System.identityHashCode(next);
+				if (visited.contains("@" + hash)) {
+					return true;
+				} else {
+					visited.add("@" + hash);
+				}
+				next = next.next;
+			}
+			return false;
+		}
+	}
+}

src/main/java/Node.java

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+
+
+public class Node {
+	int data;
+	public Node next;
+
+	public Node(int data, Node next) {
+		this.data = data;
+		this.next = next;
+	}
+}

test/main/java/LinkedListsDetectCycleTest.java

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+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * @author medany
+ */
+
+public class LinkedListsDetectCycleTest {
+
+	@Test
+	public void Test_True() {
+
+		LinkedListsDetectCycle alg = new LinkedListsDetectCycle();
+
+		Node head = new Node(1, new Node(2, new Node(3, null)));
+		head.next.next.next = head.next;
+
+		boolean actual = alg.solve(head), expected = true;
+
+		Assert.assertEquals(expected, actual);
+
+	}
+
+	@Test
+	public void Test_False() {
+
+		LinkedListsDetectCycle alg = new LinkedListsDetectCycle();
+
+		Node head = new Node(1, null);
+
+		boolean actual = alg.solve(head), expected = false;
+
+		Assert.assertEquals(expected, actual);
+
+	}
+
+}