reverse dll and insert element in between

Author: premaseem

src/codechallenge/linkedlist/InsertNodeInSortedLL.java

@@ -0,0 +1,93 @@
+package codechallenge.linkedlist;
+
+import me.premaseem.reusable.MyDLLNode;
+import org.junit.Test;
+
+/*
+
+Challenge: Inserting a Node Into a Sorted Doubly Linked List
+ 1. Empty list
+ 2. At the beginning of the list
+ 3. Somewhere at the middle of the list
+ 4. At the end of the list
+ */
+
+
+public class InsertNodeInSortedLL {
+
+    // Test Driven Development by Aseem Jain
+    @Test
+    public void test() {
+        MyDLLNode n1 = new MyDLLNode(-100);
+        MyDLLNode n2 = new MyDLLNode(0);
+        MyDLLNode n3 = new MyDLLNode(70);
+        MyDLLNode n4 = new MyDLLNode(10000);
+
+        n1.next = n2;
+        n2.next = n3;
+        n3.next = n4;
+
+        n4.prev = n3;
+        n3.prev = n2;
+        n2.prev = n1;
+
+        sortedInsert(n1, 250);
+        assert n3.next.data == 250;
+        assert n4.prev.data == 250;
+
+        sortedInsert(n1, 250000);
+        assert n4.next.data == 250000;
+
+    }
+
+
+    // Using Recursion
+    MyDLLNode sortedInsertR(MyDLLNode head, int data) {
+        if (head == null) {
+            return new MyDLLNode(data);
+        } else if (data <= head.data) {
+            MyDLLNode n = new MyDLLNode(data);
+            n.next = head;
+            head.prev = n;
+            return n;
+        } else {
+            MyDLLNode rest = sortedInsert(head.next, data);
+            head.next = rest;
+            rest.prev = head;
+            return head;
+        }
+    }
+
+    // Using Greedy algorithm
+    MyDLLNode sortedInsert(MyDLLNode head, int data) {
+        MyDLLNode nn = new MyDLLNode(data);
+        if (head == null) {
+            return nn;
+        }
+        MyDLLNode cn = head;
+
+        while(cn.next != null && cn.data < data){
+            cn = cn.next;
+        }
+
+        if(head == cn){
+            nn.next = cn;
+            cn.prev = nn;
+            return nn;
+        }
+
+        if(cn.data<data){
+            cn.next = nn;
+            nn.prev = cn;
+        }else{
+            nn.next = cn;
+            nn.prev = cn.prev;
+            cn.prev.next = nn;
+            cn.prev = nn;
+        }
+
+        return head;
+
+    }
+}
+

src/codechallenge/linkedlist/ReverseDoublyLinkedlist.java

@@ -0,0 +1,62 @@
+package codechallenge.linkedlist;
+
+import me.premaseem.reusable.MyDLLNode;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/*
+
+Challenge: Reverse a doubly linked list
+
+ */
+
+
+public class ReverseDoublyLinkedlist {
+
+    // Test Driven Development by Aseem Jain
+    @Test
+    public void test() {
+        MyDLLNode n1 = new MyDLLNode(-100);
+        MyDLLNode n2 = new MyDLLNode(0);
+        MyDLLNode n3 = new MyDLLNode(100);
+        MyDLLNode n4 = new MyDLLNode(250);
+
+        n1.next = n2;
+        n2.next = n3;
+        n3.next = n4;
+
+        n4.prev = n3;
+        n3.prev = n2;
+        n2.prev = n1;
+
+        MyDLLNode newHead = reverseLL(n1);
+
+        while(newHead.next != null){
+            System.out.println(newHead.data + "> " + newHead.next.data);
+           assert  newHead.data > newHead.next.data;
+           newHead = newHead.next;
+        }
+
+    }
+
+    private MyDLLNode reverseLL(MyDLLNode n1) {
+        List<MyDLLNode> al = new ArrayList<>();
+        while(n1 != null){
+            al.add(n1);
+            n1 = n1.next;
+        }
+
+        for (int i = al.size()-1; i > 0; i--) {
+            al.get(i).next = al.get(i-1);
+            al.get(i-1).prev = al.get(i);
+        }
+        al.get(al.size()-1).prev = null;
+        al.get(0).next = null;
+        return al.get(al.size()-1);
+    }
+
+
+}
+