implement queue using stack javascript
implement queue using stack javascript
xxxxxxxxxxfunction Queue() { this.queue = {}; this.tail = 0; this.head = 0;}// Add an element to the end of the queue.Queue.prototype.enqueue = function(element) { this.queue[this.tail++] = element;}// Delete the first element of the queue.Queue.prototype.dequeue = function() { if (this.tail === this.head) return undefined var element = this.queue[this.head]; delete element; return element;}Source: www.telerik.com
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xxxxxxxxxxclass CrazyQueue { constructor() { // Initialize two stacks to represent the queue this.stackNewOnTop = []; // Newest elements are at the top of this stack this.stackOldestOnTop = []; // Oldest elements are at the top of this stack } // Add an element to the back of the queue enqueue(value) { console.log("we enqueued " + value); return this.stackNewOnTop.push(value); } // Transfer elements from stackNewOnTop to stackOldestOnTop if necessary, and remove the oldest element from the queue dequeue() { if (this.stackOldestOnTop.length === 0) { // If stackOldestOnTop is empty, transfer elements from stackNewOnTop to stackOldestOnTop to reverse the order this.shiftStacks(); } console.log("we dequeued " + this.stackOldestOnTop.pop()); } // Peek at the oldest element in the queue without removing it peek() { if (this.stackOldestOnTop.length === 0) { // If stackOldestOnTop is empty, transfer elements from stackNewOnTop to stackOldestOnTop to reverse the order this.shiftStacks(); } return this.stackOldestOnTop[this.stackOldestOnTop.length - 1]; // Return the top element of stackOldestOnTop } // Transfer elements from stackNewOnTop to stackOldestOnTop to reverse the order of elements in the queue shiftStacks() { const length = this.stackNewOnTop.length; for (let i = 0; i < length; i++) { this.stackOldestOnTop.push(this.stackNewOnTop.pop()); } } // Print the contents of the two stacks (for debugging purposes) printer() { console.log("this is the stack with newest in front : " + this.stackNewOnTop); console.log("this is the stack with oldest in front : " + this.stackOldestOnTop); }}// Test the CrazyQueue classconst myQueue = new CrazyQueue();myQueue.enqueue(14);myQueue.enqueue(12);myQueue.enqueue(11);console.log("Peek: " + myQueue.peek()); // should output 14myQueue.dequeue();myQueue.enqueue(22);console.log("Peek: " + myQueue.peek()); // should output 12myQueue.dequeue();myQueue.dequeue();console.log("Peek: " + myQueue.peek()); // should output 22myQueue.dequeue();myQueue.enqueue(22);myQueue.enqueue(242);myQueue.dequeue();myQueue.enqueue(22);myQueue.dequeue();console.log(myQueue);Source: Grepper
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