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82 lines
1.8 KiB
Markdown
82 lines
1.8 KiB
Markdown
---
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title: Create a Circular Queue
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---
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## Create a Circular Queue
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### Method:
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- In this challenge we create a Circular Queue data structure.
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- First, we need to create an array of `size` with all elements set to `null`.
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- Then we create an equeue method, which moves the write pointer but doesnt exceed the read pointer.
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- The dequeue method on the other hand, moves the read pointer but doesnt exceed the write pointer.
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- Example:
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- First, we create an array of length 5:
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```shell
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[null, null, null, null, null]
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^Read @ 0
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^Write @ 0
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```
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- Then we enqueue `a`, `b`, and `c`:
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```shell
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[a, b, c, null, null]
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^Read @ 0
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^Write @ 3
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```
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- Now we dequeue all the enqueued items:
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```shell
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[null, null, null, null, null]
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^Read @ 3
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^Write @ 3
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```
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- Finally, we enqueue `d`, `e` and `f`:
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```shell
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[f, null, null, d, e]
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^Read @ 3
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^Write @ 1
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```
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### Solution:
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```js
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class CircularQueue {
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constructor(size) {
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this.queue = [];
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this.read = 0;
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this.write = 0;
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this.max = size - 1;
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while (size > 0) {
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this.queue.push(null);
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size--;
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}
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}
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print() {
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return this.queue;
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}
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enqueue(item) {
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if (this.queue[this.write] === null){
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this.queue[this.write++] = item;
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if (this.write > this.max) this.write = 0;
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return item;
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}
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return null;
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}
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dequeue() {
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if (this.queue[this.read] != null){
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let item = this.queue[this.read];
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this.queue[this.read++] = null;
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if (this.read > this.max) this.read = 0;
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return item;
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}
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return null;
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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/Circular_buffer)
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