Create BST to LL

Author: akshayavb99

Course 2 - Data Structures in JAVA/Lecture 13 - BST I/BST to LL

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+/*
+Given a BST, convert it into a sorted linked list. You have to return the head of LL.
+
+Input format:
+The first and only line of input contains data of the nodes of the tree in level order form. The data of the nodes of the tree is separated by space. If any node does not have left or right child, take -1 in its place. Since -1 is used as an indication whether the left or right nodes exist, therefore, it will not be a part of the data of any node.   
+
+Output Format:
+The first and only line of output prints the elements of sorted linked list.
+
+Constraints:
+Time Limit: 1 second
+
+Sample Input 1:
+8 5 10 2 6 -1 -1 -1 -1 -1 7 -1 -1
+Sample Output 1:
+2 5 6 7 8 10
+*/
+class PassNode<T>
+{
+	T head;
+    T tail;
+}
+public class Solution {
+
+	/*
+	 * Binary Tree Node class
+	 * 
+	 * class BinaryTreeNode<T> { T data; BinaryTreeNode<T> left; BinaryTreeNode<T>
+	 * right;
+	 * 
+	 * public BinaryTreeNode(T data) { this.data = data; } }
+	 */
+
+	/*
+	 * LinkedList Node Class
+	 *
+	 * 
+	 * class LinkedListNode<T> { T data; LinkedListNode<T> next;
+	 * 
+	 * public LinkedListNode(T data) { this.data = data; } }
+	 */
+
+	public static LinkedListNode<Integer> constructLinkedList(BinaryTreeNode<Integer> root) {
+        PassNode<LinkedListNode<Integer>> passNode= constructLinkedListHelper(root);
+        return passNode.head;
+	}
+    
+    public static PassNode<LinkedListNode<Integer>> constructLinkedListHelper(BinaryTreeNode<Integer> root)
+    {
+    	if(root==null)
+        {
+            return new PassNode<LinkedListNode<Integer>>();
+        }
+        
+        if (root.left==null && root.right==null)
+        {
+        	PassNode<LinkedListNode<Integer>> passNode = new PassNode<LinkedListNode<Integer>>();
+        	passNode.head=new LinkedListNode<Integer>(root.data);
+            passNode.tail=null;
+            return passNode;
+        }
+        
+        PassNode<LinkedListNode<Integer>> passNodeLeft = constructLinkedListHelper(root.left);
+        PassNode<LinkedListNode<Integer>> passNodeRight = constructLinkedListHelper(root.right);
+        PassNode<LinkedListNode<Integer>> passNode = new PassNode<LinkedListNode<Integer>>();
+        LinkedListNode<Integer> newNode=new LinkedListNode<Integer>(root.data);
+        
+        if (passNodeLeft.head==null)
+        {
+        	passNode.head=newNode;
+            //passNode.tail=newNode;
+        }
+        else
+        {
+        	passNode.head=passNodeLeft.head;
+        }
+        
+        if(passNodeLeft.tail==null)
+        {
+        	passNode.head.next=newNode;
+            passNode.tail=newNode;
+        }
+        else
+        {
+        	passNodeLeft.tail.next=newNode;
+            passNode.tail=newNode;
+        }
+        
+        if (passNodeRight.head!=null)
+        {
+        	passNode.tail.next=passNodeRight.head;
+            passNode.tail=passNodeRight.head;
+        }
+        
+        if(passNodeRight.tail!=null)
+        {
+        	passNode.tail=passNodeRight.tail;
+        }
+    
+        return passNode;
+   
+    }
+}
+