2020-10-02 22:15:29 +05:30
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// Circular Queues offer a quick to store FIFO data with a maximum size.
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// Conserves memory as we only store up to our capacity
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// It is opposed to a queue which could continue to grow if input outpaces output
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// Doesn’t use dynamic memory so No memory leaks
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class CircularQueue {
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2023-10-03 23:08:19 +02:00
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constructor(maxLength) {
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2020-10-02 22:15:29 +05:30
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this.queue = []
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this.front = 0
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this.rear = 0
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this.maxLength = maxLength
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}
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// ADD ELEMENTS TO QUEUE
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2023-10-03 23:08:19 +02:00
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enqueue(value) {
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2020-10-02 22:15:29 +05:30
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if (this.checkOverflow()) return
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if (this.checkEmpty()) {
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this.front += 1
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this.rear += 1
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} else {
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if (this.rear === this.maxLength) {
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this.rear = 1
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} else this.rear += 1
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}
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this.queue[this.rear] = value
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}
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// REMOVES ELEMENTS
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dequeue() {
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2020-10-02 22:15:29 +05:30
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if (this.checkEmpty()) {
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// UNDERFLOW
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2020-10-02 22:15:29 +05:30
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return
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}
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const y = this.queue[this.front]
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this.queue[this.front] = '*'
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2021-10-21 22:59:56 +05:30
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if (!this.checkSingleelement()) {
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2020-10-02 22:15:29 +05:30
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if (this.front === this.maxLength) this.front = 1
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else {
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this.front += 1
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}
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}
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return y // Returns the removed element and replaces it with a star
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}
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// checks if the queue is empty or not
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checkEmpty() {
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2020-10-02 22:15:29 +05:30
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if (this.front === 0 && this.rear === 0) {
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return true
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}
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}
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2023-10-03 23:08:19 +02:00
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checkSingleelement() {
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2020-10-02 22:15:29 +05:30
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if (this.front === this.rear && this.rear !== 0) {
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this.front = this.rear = 0
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return true
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}
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}
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// Checks if max capacity of queue has been reached or not
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checkOverflow() {
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if (
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(this.front === 1 && this.rear === this.maxLength) ||
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this.front === this.rear + 1
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) {
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2021-10-10 16:11:06 +02:00
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// CIRCULAR QUEUE OVERFLOW
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2020-10-02 22:15:29 +05:30
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return true
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}
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}
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2021-10-10 16:11:06 +02:00
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// Prints the entire array ('*' represents blank space)
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display(output = (value) => console.log(value)) {
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for (let index = 1; index < this.queue.length; index++) {
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output(this.queue[index])
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2020-10-02 22:15:29 +05:30
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}
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}
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// Displays the length of queue
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length() {
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2020-10-02 22:15:29 +05:30
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return this.queue.length - 1
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}
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// Display the top most value of queue
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peek() {
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return this.queue[this.front]
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}
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}
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2021-10-10 16:11:06 +02:00
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export { CircularQueue }
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