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@mohitsharma93
Last active May 8, 2021
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JavaScript presentation of queue data structure
/**
* A queue can remove only the most recently added value, what if we need to remove old value. here comes another
* data structure QUEUE.
* queue is work on FIRST IN FIRST OUT
*
* queue is work on LAST IN FIRST OUT principle.
* queue is just like array with only capabilities of push and pop (method).
* [6]
* [5]
* [4]
* [3]
* [2]
* [1] ----> which is first element of queue
* @method
* enqueue: adds value to a queue return size of queue
* dequeue: removes value from queue and return removed value.
*
* own added methods.
* size: return size of queue.
* contains: return boolean value wether value exist in queue or not.
*/
class Queue {
constructor() {
this._start = 0;
this._end = 0; // hold
this._storage = {};
}
}
/**
* add element to stack.
* 1. increment the queue _end count.
* 2. to retain the order in which it was added, we use _end as key.
* @param value
* @return updated stack
*/
Queue.prototype.enqueue = function(value) {
this._storage[this._end] = value;
this._end += 1;
return this.size();
}
/**
* @return removed element
*/
Queue.prototype.dequeue = function() {
var element = this._storage[this._start];
delete this._storage[this._start];
if (this._start < this._end) {
// When _start is equal to _end it means there are no elements in the queue.
// There is no need to increase _start if there are no elements.
// _start can't be greater than _end, that is why we only increment _start if _start is lower than _end.
// We make sure that _start is always pointing to a number equal or lower than _end.
this.start += 1;
}
return element;
}
/**
* @return last element of stack.
*/
Queue.prototype.peek = function() {
return this._storage[this._start]
}
/**
* get stack
*/
Queue.prototype.getQueue = function () {
return this._storage;
}
/**
* get count
*/
Queue.prototype.size = function () {
return this._end;
}
/**
* loop until _end is smaller than to _start
* @param {*} value
* @returns boolean
*/
Queue.prototype.contains = function(value) {
for (var i = this._start; i < this._end; i++) {
if (this._storage[i] === value) return true;
}
return false;
};
let stack = new Queue();
console.log(stack.getQueue());
console.log(stack.enqueue(1));
console.log(stack.enqueue(2));
console.log(stack.dequeue());
console.log(stack.enqueue(3));
console.log(stack.enqueue([1, 2, 3, 4]));
console.log(stack.dequeue())
console.log(stack.getQueue());
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