tree questions

Author: kunal-kushwaha

lectures/20-trees/code/Advance questions/DoubleLinkedList.java

@@ -0,0 +1,57 @@
+public class DoubleLinkedList {
+ LLNode head;
+ LLNode tail;
+
+ public TreeNode convert(TreeNode root) {
+ if (root == null) {
+ return null;
+ }
+
+ helper(root);
+
+ return head;
+ }
+
+ private void helper(TreeNode node) {
+ if(node == null) {
+ return null;
+ }
+
+ helper(node.left);
+
+
+ LLNode newNode = new LLNode(node.val);
+
+ if(head == null) {
+ head = newNode;
+ tail = newNode;
+ } else {
+ tail.next = newNode;
+ newNode.prev = tail;
+ tail = newNode;
+ }
+ 
+ helper(node.right);
+ 
+ }
+}
+
+class LLNode {
+ int val;
+ LLNode prev;
+ LLNode next;
+
+ public LLNode (int val) {
+ this.val = val;
+ }
+}
+
+class TreeNode {
+ int val;
+ TreeNode left;
+ TreeNode right;
+
+ public TreeNode (int val) {
+ this.val = val;
+ }
+}

lectures/20-trees/code/Advance questions/TwoNodeSwap.java

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+import java.util.*;
+
+class Node {
+ int val;
+ Node left; 
+ Node right;
+ public Node (int val) {
+ this.val = val;
+ }
+}
+
+public class TwoNodeSwap {
+ Node first;
+ Node second;
+ Node prev;
+
+ public void helper(Node root) {
+ iot(root);
+
+ // swap
+ int temp = first.val;
+ first.val = second.val;
+ second.val = temp;
+ }
+
+ private void iot(Node node) {
+ if(node == null) {
+ return;
+ }
+
+ iot(node.left);
+
+ if(prev != null && prev.val > node.val) {
+ if(first == null) {
+ first = prev;
+ }
+ second = node;
+ }
+
+ prev = node;
+ 
+ iot(node.right);
+ }
+
+ public void printIOT(Node node) {
+ if(node == null) {
+ return;
+ }
+ printIOT(node.left);
+ System.out.print(node.val + " ");
+ printIOT(node.right);
+ }
+}