Add solution #382

Author: JoshCrozier

README.md

@@ -300,6 +300,7 @@
 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|
+382|[Linked List Random Node](./0382-linked-list-random-node.js)|Medium|
 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|

solutions/0382-linked-list-random-node.js

@@ -0,0 +1,46 @@
+/**
+ * 382. Linked List Random Node
+ * https://leetcode.com/problems/linked-list-random-node/
+ * Difficulty: Medium
+ *
+ * Given a singly linked list, return a random node's value from the linked list. Each node must
+ * have the same probability of being chosen.
+ *
+ * Implement the Solution class:
+ * - Solution(ListNode head) Initializes the object with the head of the singly-linked list head.
+ * - int getRandom() Chooses a node randomly from the list and returns its value. All the nodes
+ *   of the list should be equally likely to be chosen.
+ */
+
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val, next) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.next = (next===undefined ? null : next)
+ * }
+ */
+/**
+ * @param {ListNode} head
+ */
+var Solution = function(head) {
+  this.head = head;
+};
+
+/**
+ * @return {number}
+ */
+Solution.prototype.getRandom = function() {
+  let current = this.head;
+  let result = current.val;
+  let count = 1;
+
+  while (current.next) {
+    current = current.next;
+    count++;
+    if (Math.random() < 1 / count) {
+      result = current.val;
+    }
+  }
+
+  return result;
+};