feat: Solving "Number of recent calls" (LeetCode | #933 | Easy)

Author: brianr482

stacks-queues/number-recent-calls.js

@@ -0,0 +1,75 @@
+/**
+ * LeetCode | #933 | Easy
+ * 
+ * You have a RecentCounter class which counts the number of recent requests within a certain time frame.
+ * 
+ * Implement the RecentCounter class:
+ * - RecentCounter() Initializes the counter with zero recent requests.
+ * - int ping(int t) Adds a new request at time t, where t represents some time in milliseconds, and returns
+ * the number of requests that has happened in the past 3000 milliseconds (including the new request).
+ * Specifically, return the number of requests that have happened in the inclusive range [t - 3000, t].
+ * 
+ * It is guaranteed that every call to ping uses a strictly larger value of t than the previous call.
+ * 
+ * Constraints:
+ * - 1 <= t <= 10^9
+ * - Each test case will call ping with strictly increasing values of t.
+ * - At most 10^4 calls will be made to ping.
+ * 
+ */
+
+
+/**
+ * Solution 1 (slowest -- resembling a queue with "shift" which is slow)
+ * Time Complexity: O(n) - Space complexity: ?
+ */
+
+const RecentCounter = function () {
+  this.recentReqsQueue = [];
+};
+
+/** 
+* @param {number} t
+* @return {number}
+*/
+RecentCounter.prototype.ping = function (t) {
+  this.recentReqsQueue.push(t);
+  const minRangeVal = Math.max(t - 3000, 0);
+
+  while (this.recentReqsQueue.length > 0 && this.recentReqsQueue[0] < minRangeVal) {
+    this.recentReqsQueue.shift();
+  }
+
+  return this.recentReqsQueue.length;
+};
+
+/**
+ * Solution 2 (fastest -- resembling a queue behaviour by using a pointer)
+ * Time Complexity: O(n) - Space complexity: O(n)
+ */
+
+const RecentCounter2 = function () {
+  this.i = 0;
+  this.recentReqsQueue = [];
+};
+
+/** 
+* @param {number} t
+* @return {number}
+*/
+RecentCounter2.prototype.ping = function (t) {
+  this.recentReqsQueue.push(t);
+  const minRangeVal = Math.max(t - 3000, 0);
+
+  while (this.recentReqsQueue.length > 0 && this.recentReqsQueue[this.i] < minRangeVal) {
+    this.i++;
+  }
+
+  return this.recentReqsQueue.length - this.i;
+};
+
+/** 
+* Your RecentCounter object will be instantiated and called as such:
+* var obj = new RecentCounter()
+* var param_1 = obj.ping(t)
+*/