97 lines
2.5 KiB
JavaScript
97 lines
2.5 KiB
JavaScript
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class Task {
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constructor(priority, name) {
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this.priority = priority;
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this.name = name;
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}
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toString() {
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return `${this.priority}, ${this.name}`;
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}
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}
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class PriorityQueue {
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constructor() {
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this.heap = [];
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}
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// Add a task to the heap
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add(task) {
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this.heap.push(task);
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this.bubbleUp(this.heap.length - 1);
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}
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// Remove and return the highest priority task
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remove() {
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if (this.heap.length === 0) return null;
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const min = this.heap[0];
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const end = this.heap.pop();
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if (this.heap.length > 0) {
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this.heap[0] = end;
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this.bubbleDown(0);
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}
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return min;
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}
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// Check if the queue is empty
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isEmpty() {
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return this.heap.length === 0;
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}
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// Move the element at index `i` up the heap
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bubbleUp(i) {
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const element = this.heap[i];
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while (i > 0) {
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const parentIndex = Math.floor((i - 1) / 2);
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const parent = this.heap[parentIndex];
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if (element.priority >= parent.priority) break;
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this.heap[i] = parent;
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i = parentIndex;
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}
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this.heap[i] = element;
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}
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// Move the element at index `i` down the heap
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bubbleDown(i) {
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const element = this.heap[i];
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const length = this.heap.length;
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while (true) {
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const leftChildIndex = 2 * i + 1;
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const rightChildIndex = 2 * i + 2;
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let leftChild, rightChild;
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let swap = null;
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if (leftChildIndex < length) {
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leftChild = this.heap[leftChildIndex];
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if (leftChild.priority < element.priority) {
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swap = leftChildIndex;
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}
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}
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if (rightChildIndex < length) {
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rightChild = this.heap[rightChildIndex];
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if (
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(swap === null && rightChild.priority < element.priority) ||
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(swap !== null && rightChild.priority < leftChild.priority)
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) {
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swap = rightChildIndex;
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}
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}
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if (swap === null) break;
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this.heap[i] = this.heap[swap];
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i = swap;
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}
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this.heap[i] = element;
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}
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}
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// Usage
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const pq = new PriorityQueue();
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pq.add(new Task(3, "Clear drains"));
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pq.add(new Task(4, "Feed cat"));
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pq.add(new Task(5, "Make tea"));
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pq.add(new Task(1, "Solve RC tasks"));
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pq.add(new Task(2, "Tax return"));
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while (!pq.isEmpty()) {
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console.log(pq.remove().toString());
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}
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