81 lines
2.2 KiB
Markdown
81 lines
2.2 KiB
Markdown
---
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title: Create a Queue Class
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---
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## Create a Queue Class
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### Method:
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- A Queue is an abstract Data Structure.
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- A Queue folow FIFO/LILO principle.
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- In this challenge we nede to implement `enqueue()`, `dequeue()`, `front()`, `size()`, `isEmpty()` methods.
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- `enqueue()` - This method adds the element to the queue.
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- `dequeue()` - This method removes the first element from the queue.
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- `front()` - This method returns the first element in the queue that'd be dequeue'd.
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- `size()` - This method returns the size of the queue.
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- `isEmpty()` - This method returns if the queue is empty.
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-
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| DS | Access | Search | Insert | Delete |
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| ----- | ------ | ------ | ------ | ------ |
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| Queue | n | n | 1 | 1 |
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- 
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### Solution:
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#### Basic:
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##### Note:
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- This solution is not exactly a queue, the shift() method used in the dequeue() method is of complexity `O(n)` and not `O(1)`. However, the advanced solution rectifies this and uses Object(HashTables) instead of Array to implement Queue.
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```js
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function Queue () {
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var collection = [];
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this.print = function() {
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console.log(collection);
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};
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this.enqueue = function(val){
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collection.push(val);
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};
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this.dequeue = function(){
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return collection.shift();
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}
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this.front = function(){
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return collection[0];
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}
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this.size = function(){
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return collection.length;
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}
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this.isEmpty = function(){
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return collection.length === 0;
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}
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}
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```
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#### Advanced - ES6 class syntax:
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```js
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class Queue {
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constructor(){
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this.collection = {};
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this.start = 0;
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this.end = 0;
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}
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print(){
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console.log(this.collection);
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}
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enqueue(val){
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this.collection[this.end++] = val;
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}
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dequeue(){
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return this.collection[this.start++];
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}
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front(){
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return this.collection[this.start];
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}
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size(){
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return this.end - this.start;
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}
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isEmpty(){
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return this.size() === 0;
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}
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}
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```
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### References:
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- [Wikipedia](https://en.wikipedia.org/wiki/Queue_(abstract_data_type))
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