feat: Impelement queue 2 stacks

  - Hackerrank

Author: brianr482

queue-2-stacks.js

@@ -0,0 +1,92 @@
+/**
+ * Hackerrank
+ * A queue is an abstract data type that maintains the order in which elements
+ * were added to it, allowing the oldest elements to be removed from the front
+ * and new elements to be added to the rear. This is called a First-In-First-Out
+ * (FIFO) data structure because the first element added to the queue (i.e., the
+ * one that has been waiting the longest) is always the first one to be removed.
+ * 
+ * In this challenge, you must first implement a queue using two stacks. Then
+ * process q queries, where each query is one of the following  types:
+ * 
+ * 1 x: Enqueue element x into the end of the queue.
+ * 2: Dequeue the element at the front of the queue.
+ * 3: Print the element at the front of the queue.
+ * 
+ * Constraints:
+ * 1. 1 <= q <= 10^5
+ * 2. 1 <= type <= 3
+ * 3. 1 <= |x| <= 10^9
+ * 
+ * This solution got 25 points
+ * Problem link: http://hr.gs/acbfeb
+ */
+class Queue {
+  constructor() {
+    this.principalStack = [];
+    this.auxStack = [];
+  }
+
+  /**
+   * Fill the auxiliar stack which is contains
+   * a reversed list of the main stack elements
+   */
+  fillAux() {
+    if (this.auxStack.length === 0) {
+      while(this.principalStack.length > 0) {
+        this.auxStack.push(this.principalStack.pop())
+      }
+    }
+  }
+  
+  /**
+   * Insert a new element in the rear of the queue
+   */
+  enqueue(value) {
+    this.principalStack.push(value);
+  }
+
+  /**
+   * Remove the head element of the queue
+   */
+  dequeue() {
+    this.fillAux();
+    this.auxStack.pop();
+  }
+
+  /**
+   * Print the rear element of the queue
+   */
+  printRear() {
+    this.fillAux();
+    const head = this.auxStack.pop();
+    console.log(head);
+    this.auxStack.push(head)
+  }
+}
+/**
+ * 
+ * @param {string} input - Queries to bo processed  
+ */
+function processData(input) {
+  const ACTIONS = {
+    ENQEUE: '1',
+    DEQUEUE: '2',
+    PRINT: '3'
+  };
+  const queue = new Queue();
+  input.split('\n').forEach(line => {
+    const query = line.split(' ');
+    switch (query[0]) {
+      case ACTIONS.ENQEUE:
+        queue.enqueue(query[1]);
+        break;
+      case ACTIONS.DEQUEUE:
+        queue.dequeue();
+        break;
+      case ACTIONS.PRINT:
+        queue.printRear();
+        break;
+    }
+  })
+}