Add solution #919

Author: JoshCrozier

README.md

@@ -728,6 +728,7 @@
 915|[Partition Array into Disjoint Intervals](./solutions/0915-partition-array-into-disjoint-intervals.js)|Medium|
 916|[Word Subsets](./solutions/0916-word-subsets.js)|Medium|
 918|[Maximum Sum Circular Subarray](./solutions/0918-maximum-sum-circular-subarray.js)|Medium|
+919|[Complete Binary Tree Inserter](./solutions/0919-complete-binary-tree-inserter.js)|Medium|
 922|[Sort Array By Parity II](./solutions/0922-sort-array-by-parity-ii.js)|Easy|
 925|[Long Pressed Name](./solutions/0925-long-pressed-name.js)|Easy|
 926|[Flip String to Monotone Increasing](./solutions/0926-flip-string-to-monotone-increasing.js)|Medium|

solutions/0919-complete-binary-tree-inserter.js

@@ -0,0 +1,66 @@
+/**
+ * 919. Complete Binary Tree Inserter
+ * https://leetcode.com/problems/complete-binary-tree-inserter/
+ * Difficulty: Medium
+ *
+ * A complete binary tree is a binary tree in which every level, except possibly the last,
+ * is completely filled, and all nodes are as far left as possible.
+ *
+ * Design an algorithm to insert a new node to a complete binary tree keeping it complete
+ * after the insertion.
+ *
+ * Implement the CBTInserter class:
+ * - CBTInserter(TreeNode root) Initializes the data structure with the root of the complete
+ *   binary tree.
+ * - int insert(int v) Inserts a TreeNode into the tree with value Node.val == val so that
+ *   the tree remains complete, and returns the value of the parent of the inserted TreeNode.
+ * - TreeNode get_root() Returns the root node of the tree.
+ */
+
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ */
+var CBTInserter = function(root) {
+  this.root = root;
+  this.deque = [];
+
+  const queue = [root];
+  while (queue.length) {
+    const node = queue.shift();
+    if (!node.left || !node.right) this.deque.push(node);
+    if (node.left) queue.push(node.left);
+    if (node.right) queue.push(node.right);
+  }
+};
+
+/**
+ * @param {number} val
+ * @return {number}
+ */
+CBTInserter.prototype.insert = function(val) {
+  const node = new TreeNode(val);
+  const parent = this.deque[0];
+  if (!parent.left) {
+    parent.left = node;
+  } else {
+    parent.right = node;
+    this.deque.shift();
+  }
+  this.deque.push(node);
+  return parent.val;
+};
+
+/**
+ * @return {TreeNode}
+ */
+CBTInserter.prototype.get_root = function() {
+  return this.root;
+};