Add solution #901

Author: JoshCrozier

README.md

@@ -248,6 +248,7 @@
 876|[Middle of the Linked List](./0876-middle-of-the-linked-list.js)|Easy|
 884|[Uncommon Words from Two Sentences](./0884-uncommon-words-from-two-sentences.js)|Easy|
 890|[Find and Replace Pattern](./0890-find-and-replace-pattern.js)|Medium|
+901|[Online Stock Span](./0901-online-stock-span.js)|Medium|
 905|[Sort Array By Parity](./0905-sort-array-by-parity.js)|Easy|
 914|[X of a Kind in a Deck of Cards](./0914-x-of-a-kind-in-a-deck-of-cards.js)|Medium|
 916|[Word Subsets](./0916-word-subsets.js)|Medium|

solutions/0901-online-stock-span.js

@@ -0,0 +1,46 @@
+/**
+ * 901. Online Stock Span
+ * https://leetcode.com/problems/online-stock-span/
+ * Difficulty: Medium
+ *
+ * Design an algorithm that collects daily price quotes for some stock and returns the
+ * span of that stock's price for the current day.
+ *
+ * The span of the stock's price in one day is the maximum number of consecutive days
+ * (starting from that day and going backward) for which the stock price was less than
+ * or equal to the price of that day.
+ *
+ * - For example, if the prices of the stock in the last four days is [7,2,1,2] and the
+ *   price of the stock today is 2, then the span of today is 4 because starting from
+ *   today, the price of the stock was less than or equal 2 for 4 consecutive days.
+ *
+ * - Also, if the prices of the stock in the last four days is [7,34,1,2] and the price
+ *   of the stock today is 8, then the span of today is 3 because starting from today,
+ *   the price of the stock was less than or equal 8 for 3 consecutive days.
+ *
+ * Implement the StockSpanner class:
+ * - StockSpanner() Initializes the object of the class.
+ * - int next(int price) Returns the span of the stock's price given that today's
+ *   price is price.
+ */
+
+var StockSpanner = function() {
+  this.stack = [];
+};
+
+/**
+ * @param {number} price
+ * @return {number}
+ */
+StockSpanner.prototype.next = function(price) {
+  let count = 1;
+
+  while (this.stack.length && price >= this.stack[this.stack.length - 1][0]) {
+    count += this.stack[this.stack.length - 1][1];
+    this.stack.pop();
+  }
+
+  this.stack.push([price, count]);
+
+  return count;
+};