Populating Next Right Pointers in Each Node II : Accepted

Author: gouthampradhan

README.md

@@ -200,6 +200,7 @@ My accepted leetcode solutions to some of the common interview problems.
 - [Construct String From Binary Tree](problems/src/tree/ConstructStringFromBinaryTree.java) (Easy)
 - [Flatten Binary Tree to Linked List](problems/src/tree/FlattenBinaryTree.java) (Medium)
 - [Populating Next Right Pointers in Each Node](problems/src/tree/NextRightPointer.java) (Medium)
+- [Populating Next Right Pointers in Each Node II](problems/src/tree/NextRightPointerII.java) (Medium)
 - [Subtree of Another Tree](problems/src/tree/SubtreeOfAnotherTree.java) (Easy)
 - [Binary Tree Zigzag Level Order Traversal](problems/src/tree/ZigZagTraversal.java) (Medium)
 - [Binary Tree Inorder Traversal](problems/src/tree/BinaryTreeInorderTraversal.java) (Medium)

problems/src/tree/NextRightPointerII.java

@@ -0,0 +1,74 @@
+package tree;
+
+/**
+ * Created by gouthamvidyapradhan on 03/10/2017.
+ * <p>
+ * Follow up for problem "Populating Next Right Pointers in Each Node".
+ * <p>
+ * What if the given tree could be any binary tree? Would your previous solution still work?
+ * <p>
+ * Note:
+ * <p>
+ * You may only use constant extra space.
+ * For example,
+ * Given the following binary tree,
+ * 1
+ * /  \
+ * 2    3
+ * / \    \
+ * 4   5    7
+ * After calling your function, the tree should look like:
+ * 1 -> NULL
+ * /  \
+ * 2 -> 3 -> NULL
+ * / \    \
+ * 4-> 5 -> 7 -> NULL
+ */
+public class NextRightPointerII {
+
+    public static void main(String[] args) throws Exception {
+        TreeLinkNode root = new TreeLinkNode(1);
+        root.left = new TreeLinkNode(2);
+        root.right = new TreeLinkNode(3);
+        root.right.right = new TreeLinkNode(4);
+        root.right.right.left = new TreeLinkNode(5);
+        root.right.right.right = new TreeLinkNode(6);
+        new NextRightPointerII().connect(root);
+    }
+
+    public void connect(TreeLinkNode root) {
+        TreeLinkNode prev = new TreeLinkNode(0);
+        TreeLinkNode first = null;
+        while (root != null) {
+            if (root.left != null) {
+                prev.next = root.left;
+                prev = root.left;
+                if (first == null) {
+                    first = root.left;
+                }
+            }
+            if (root.right != null) {
+                prev.next = root.right;
+                prev = root.right;
+                if (first == null) {
+                    first = root.right;
+                }
+            }
+            root = root.next;
+            if (root == null) {
+                root = first;
+                first = null;
+                prev = new TreeLinkNode(0);
+            }
+        }
+    }
+
+    public static class TreeLinkNode {
+        int val;
+        TreeLinkNode left, right, next;
+
+        TreeLinkNode(int x) {
+            val = x;
+        }
+    }
+}