solves #117 in java

Author: anishLearnsToCode

README.md

@@ -108,7 +108,7 @@
 | 113  | [Path Sum II](https://leetcode.com/problems/path-sum-ii)                                                                                                  |                                                                    [![Java](assets/java.png)](src/PathSumII.java)                                                                    |                                                                                                                                   |
 | 114  | [Flatten Binary Tree to Linked List](https://leetcode.com/problems/flatten-binary-tree-to-linked-list)                                                    |                                                          [![Java](assets/java.png)](src/FlattenBinaryTreeToLinkedList.java)                                                          |                                                                                                                                   |
 | 116  | [Populating Next Right Pointers in Each Node](https://leetcode.com/problems/populating-next-right-pointers-in-each-node)                                  |                                                      [![Java](assets/java.png)](src/PopulatingNextRightPointersInEachNode.java)                                                      |                                                                                                                                   |
-| 117  | [Populating Next Right Pointers in Each Node II](https://leetcode.com/problems/populating-next-right-pointers-in-each-node-ii)                            |                                                                                                                                                                                      |                                                                                                                                   |
+| 117  | [Populating Next Right Pointers in Each Node II](https://leetcode.com/problems/populating-next-right-pointers-in-each-node-ii)                            |                                                     [![Java](assets/java.png)](src/PopulatingNextRightPointersInEachNodeII.java)                                                     |                                                                                                                                   |
 | 118  | [Pascal's Triangle](https://leetcode.com/problems/pascals-triangle)                                                                                       |                                   [![Java](assets/java.png)](src/PascalsTriangle.java) [![Python](assets/python.png)](python/pascals_triangle.py)                                    |                                                                                                                                   |
 | 119  | [Pascal's Triangle II](https://leetcode.com/problems/pascals-triangle-ii)                                                                                 |                                 [![Java](assets/java.png)](src/PascalsTriangleII.java) [![Python](assets/python.png)](python/pascals_triangle_ii.py)                                 |                                                                                                                                   |
 | 120  | [Triangle](https://leetcode.com/problems/triangle)                                                                                                        |                                                                                                                                                                                      |                                                                                                                                   |

src/HelloWorld.java

@@ -1,17 +1,4 @@
 public class HelloWorld {
     public static void main(String[] args) {
-        PopulatingNextRightPointersInEachNode.Node root = new PopulatingNextRightPointersInEachNode.Node(1);
-        root.left = new PopulatingNextRightPointersInEachNode.Node(2);
-        root.right = new PopulatingNextRightPointersInEachNode.Node(3);
-        root.left.left = new PopulatingNextRightPointersInEachNode.Node(4);
-        root.left.right = new PopulatingNextRightPointersInEachNode.Node(5);
-        root.right.left = new PopulatingNextRightPointersInEachNode.Node(6);
-        root.right.right = new PopulatingNextRightPointersInEachNode.Node(7);
-
-        TreePrinter.print(root);
-
-        root = PopulatingNextRightPointersInEachNode.connect(root);
-
-        TreePrinter.print(root);
     }
 }

src/PopulatingNextRightPointersInEachNode.java

@@ -35,7 +35,7 @@ private static void addChildrenToQueue(Queue<Node> queue, Node root) {
         if (root.right != null) queue.add(root.right);
     }
 
-    public static class Node implements TreePrinter.PrintableNode {
+    private static class Node implements TreePrinter.PrintableNode {
         public int val;
         public Node left;
         public Node right;

src/PopulatingNextRightPointersInEachNodeII.java

@@ -0,0 +1,63 @@
+// https://leetcode.com/problems/populating-next-right-pointers-in-each-node-ii
+// T: O(n)
+// S: O(n)
+
+import java.util.LinkedList;
+import java.util.Queue;
+
+public class PopulatingNextRightPointersInEachNodeII {
+    public static Node connect(Node root) {
+        if (root == null) return null;
+
+        final Queue<Node> queue = new LinkedList<>();
+        queue.add(root);
+        queue.add(null);
+        Node previous = null;
+
+        while (!queue.isEmpty()) {
+            final Node current = queue.poll();
+            if (current == null) {
+                previous = null;
+                if (!queue.isEmpty()) queue.add(null);
+                continue;
+            }
+
+            if (previous != null) previous.next = current;
+            previous = current;
+            addChildrenToQueue(queue, current);
+        }
+
+        return root;
+    }
+
+    private static void addChildrenToQueue(Queue<Node> queue, Node root) {
+        if (root.left != null) queue.add(root.left);
+        if (root.right != null) queue.add(root.right);
+    }
+
+    private static class Node implements TreePrinter.PrintableNode {
+        public int val;
+        public Node left;
+        public Node right;
+        public Node next;
+
+        public Node(int val) {
+            this.val = val;
+        }
+
+        @Override
+        public TreePrinter.PrintableNode getLeft() {
+            return left;
+        }
+
+        @Override
+        public TreePrinter.PrintableNode getRight() {
+            return right;
+        }
+
+        @Override
+        public String getText() {
+            return val + "";
+        }
+    }
+}