Add solution #381

Author: JoshCrozier

0381-insert-delete-getrandom-o1-duplicates-allowed.js

@@ -0,0 +1,74 @@
+/**
+ * 381. Insert Delete GetRandom O(1) - Duplicates allowed
+ * https://leetcode.com/problems/insert-delete-getrandom-o1-duplicates-allowed/
+ * Difficulty: Hard
+ *
+ * RandomizedCollection is a data structure that contains a collection of numbers, possibly
+ * duplicates (i.e., a multiset). It should support inserting and removing specific elements
+ * and also reporting a random element.
+ *
+ * Implement the RandomizedCollection class:
+ * - RandomizedCollection() Initializes the empty RandomizedCollection object.
+ * - bool insert(int val) Inserts an item val into the multiset, even if the item is already
+ *   present. Returns true if the item is not present, false otherwise.
+ * - bool remove(int val) Removes an item val from the multiset if present. Returns true if
+ *   the item is present, false otherwise. Note that if val has multiple occurrences in the
+ *   multiset, we only remove one of them.
+ * - int getRandom() Returns a random element from the current multiset of elements. The
+ *   probability of each element being returned is linearly related to the number of the same
+ *   values the multiset contains.
+ *
+ * You must implement the functions of the class such that each function works on average O(1)
+ * time complexity.
+ *
+ * Note: The test cases are generated such that getRandom will only be called if there is at
+ * least one item in the RandomizedCollection.
+ */
+
+var RandomizedCollection = function() {
+  this.values = [];
+  this.map = new Map();
+};
+
+/**
+ * @param {number} val
+ * @return {boolean}
+ */
+RandomizedCollection.prototype.insert = function(val) {
+  this.values.push(val);
+  const values = this.map.get(val) || new Set();
+  values.add(this.values.length - 1);
+  this.map.set(val, values);
+  return values.size === 1;
+};
+
+/**
+ * @param {number} val
+ * @return {boolean}
+ */
+RandomizedCollection.prototype.remove = function(val) {
+  if (!this.map.has(val)) return false;
+  const values = this.map.get(val);
+  const index = values.values().next().value;
+  values.delete(index);
+  if (index < this.values.length - 1) {
+    const last = this.values.pop();
+    this.values[index] = last;
+    const lastValues = this.map.get(last);
+    lastValues.delete(this.values.length);
+    lastValues.add(index);
+  } else {
+    this.values.pop();
+  }
+  if (!values.size) {
+    this.map.delete(val);
+  }
+  return true;
+};
+
+/**
+ * @return {number}
+ */
+RandomizedCollection.prototype.getRandom = function() {
+  return this.values[Math.floor(Math.random() * this.values.length)];
+};

README.md

@@ -299,6 +299,7 @@
 377|[Combination Sum IV](./0377-combination-sum-iv.js)|Medium|
 378|[Kth Smallest Element in a Sorted Matrix](./0378-kth-smallest-element-in-a-sorted-matrix.js)|Medium|
 380|[Insert Delete GetRandom O(1)](./0380-insert-delete-getrandom-o1.js)|Medium|
+381|[Insert Delete GetRandom O(1) - Duplicates allowed](./0381-insert-delete-getrandom-o1-duplicates-allowed.js)|Hard|
 383|[Ransom Note](./0383-ransom-note.js)|Easy|
 384|[Shuffle an Array](./0384-shuffle-an-array.js)|Medium|
 387|[First Unique Character in a String](./0387-first-unique-character-in-a-string.js)|Easy|