singly & doubly linked list

src/main/java/cracking/the/code/interview/chapter4/DoublyLinkedList.java

@@ -0,0 +1,41 @@
+package cracking.the.code.interview.chapter4;
+
+public class DoublyLinkedList {
+
+
+    public static void main (String... args) {
+
+        Node n = new Node();
+        insert(n,1);
+        insert(n,2);
+        insert(n,3);
+        insert(n,4);
+        insert(n,5);
+
+    }
+
+    private static class Node {
+        Node next;
+        Node previous;
+        Integer value;
+    }
+
+    private static Node insert(Node node, int v) {
+
+        if (node.value == null) {
+            node.value = v;
+            return node;
+        }
+
+        if (node.next == null) {
+            node.next = new Node();
+            node.next.previous = node;
+        }
+
+        node.next = insert(node.next, v);
+
+        return node;
+    }
+
+
+}

src/main/java/cracking/the/code/interview/chapter4/SinglyLinkedList.java

@@ -0,0 +1,40 @@
+package cracking.the.code.interview.chapter4;
+
+public class SinglyLinkedList {
+
+
+    public static void main(String... args) {
+
+        Node root = new Node();
+
+        insert(root, 1);
+        insert(root, 2);
+        insert(root, 3);
+        insert(root, 4);
+        insert(root, 5);
+
+
+    }
+
+    private static class Node {
+        private Node next;
+        private Integer value;
+    }
+
+    private static Node insert(Node node, int v) {
+        var child = node;
+        if(child.value == null) {
+            child.value = v;
+            return child;
+        }
+
+        if(child.next == null) {
+            child.next = new Node();
+        }
+
+        child.next = insert(child.next, v);
+
+        return node;
+    }
+
+}