solve 116.populating-next-right-pointers-in-each-node

Author: andavid

vscode/116.populating-next-right-pointers-in-each-node.java

@@ -0,0 +1,110 @@
+/*
+ * @lc app=leetcode id=116 lang=java
+ *
+ * [116] Populating Next Right Pointers in Each Node
+ *
+ * https://leetcode.com/problems/populating-next-right-pointers-in-each-node/description/
+ *
+ * algorithms
+ * Medium (39.05%)
+ * Likes:    1144
+ * Dislikes: 97
+ * Total Accepted:    263.6K
+ * Total Submissions: 675.2K
+ * Testcase Example:  '{"$id":"1","left":{"$id":"2","left":{"$id":"3","left":null,"next":null,"right":null,"val":4},"next":null,"right":{"$id":"4","left":null,"next":null,"right":null,"val":5},"val":2},"next":null,"right":{"$id":"5","left":{"$id":"6","left":null,"next":null,"right":null,"val":6},"next":null,"right":{"$id":"7","left":null,"next":null,"right":null,"val":7},"val":3},"val":1}'
+ *
+ * You are given a perfect binary tree where all leaves are on the same level,
+ * and every parent has two children. The binary tree has the following
+ * definition:
+ *
+ *
+ * struct Node {
+ * ⁠ int val;
+ * ⁠ Node *left;
+ * ⁠ Node *right;
+ * ⁠ Node *next;
+ * }
+ *
+ *
+ * Populate each next pointer to point to its next right node. If there is no
+ * next right node, the next pointer should be set to NULL.
+ *
+ * Initially, all next pointers are set to NULL.
+ *
+ *
+ *
+ * Example:
+ *
+ *
+ *
+ *
+ * Input:
+ * {"$id":"1","left":{"$id":"2","left":{"$id":"3","left":null,"next":null,"right":null,"val":4},"next":null,"right":{"$id":"4","left":null,"next":null,"right":null,"val":5},"val":2},"next":null,"right":{"$id":"5","left":{"$id":"6","left":null,"next":null,"right":null,"val":6},"next":null,"right":{"$id":"7","left":null,"next":null,"right":null,"val":7},"val":3},"val":1}
+ *
+ * Output:
+ * {"$id":"1","left":{"$id":"2","left":{"$id":"3","left":null,"next":{"$id":"4","left":null,"next":{"$id":"5","left":null,"next":{"$id":"6","left":null,"next":null,"right":null,"val":7},"right":null,"val":6},"right":null,"val":5},"right":null,"val":4},"next":{"$id":"7","left":{"$ref":"5"},"next":null,"right":{"$ref":"6"},"val":3},"right":{"$ref":"4"},"val":2},"next":null,"right":{"$ref":"7"},"val":1}
+ *
+ * Explanation: Given the above perfect binary tree (Figure A), your function
+ * should populate each next pointer to point to its next right node, just like
+ * in Figure B.
+ *
+ *
+ *
+ *
+ * Note:
+ *
+ *
+ * You may only use constant extra space.
+ * Recursive approach is fine, implicit stack space does not count as extra
+ * space for this problem.
+ *
+ *
+ */
+/*
+// Definition for a Node.
+class Node {
+    public int val;
+    public Node left;
+    public Node right;
+    public Node next;
+
+    public Node() {}
+
+    public Node(int _val,Node _left,Node _right,Node _next) {
+        val = _val;
+        left = _left;
+        right = _right;
+        next = _next;
+    }
+};
+*/
+class Solution {
+  public Node connect(Node root) {
+    if (root == null) return null;
+
+    Queue<Node> queue = new LinkedList<>();
+    queue.offer(root);
+
+    while (!queue.isEmpty()) {
+      int size = queue.size();
+      Node prev = null;
+      for (int i = 0; i < size; i++) {
+        Node node = queue.poll();
+        if (prev != null) {
+          prev.next = node;
+        }
+        if (node.left != null) {
+          queue.offer(node.left);
+        }
+        if (node.right != null) {
+          queue.offer(node.right);
+        }
+        prev = node;
+      }
+      prev.next = null;
+    }
+
+    return root;
+  }
+}
+