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std/collections/binary_heap.ts

Deno standard library
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// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license./** This module is browser compatible. */
import { descend } from "./_comparators.ts";export * from "./_comparators.ts";
/** Swaps the values at two indexes in an array. */function swap<T>(array: T[], a: number, b: number) { const temp: T = array[a]; array[a] = array[b]; array[b] = temp;}
/** Returns the parent index for a child index. */function getParentIndex(index: number) { return Math.floor((index + 1) / 2) - 1;}
/** * A priority queue implemented with a binary heap. The heap is in decending order by default, * using JavaScript's built in comparison operators to sort the values. */export class BinaryHeap<T> implements Iterable<T> { #data: T[] = []; constructor(private compare: (a: T, b: T) => number = descend) {}
/** Creates a new binary heap from an array like or iterable object. */ static from<T>( collection: ArrayLike<T> | Iterable<T> | BinaryHeap<T>, ): BinaryHeap<T>; static from<T>( collection: ArrayLike<T> | Iterable<T> | BinaryHeap<T>, options: { compare?: (a: T, b: T) => number; }, ): BinaryHeap<T>; static from<T, U, V>( collection: ArrayLike<T> | Iterable<T> | BinaryHeap<T>, options: { compare?: (a: U, b: U) => number; map: (value: T, index: number) => U; thisArg?: V; }, ): BinaryHeap<U>; static from<T, U, V>( collection: ArrayLike<T> | Iterable<T> | BinaryHeap<T>, options?: { compare?: (a: U, b: U) => number; map?: (value: T, index: number) => U; thisArg?: V; }, ): BinaryHeap<U> { let result: BinaryHeap<U>; let unmappedValues: ArrayLike<T> | Iterable<T> = []; if (collection instanceof BinaryHeap) { result = new BinaryHeap( options?.compare ?? (collection as unknown as BinaryHeap<U>).compare, ); if (options?.compare || options?.map) { unmappedValues = collection.#data; } else { result.#data = Array.from(collection.#data as unknown as U[]); } } else { result = options?.compare ? new BinaryHeap(options.compare) : new BinaryHeap(); unmappedValues = collection; } const values: Iterable<U> = options?.map ? Array.from(unmappedValues, options.map, options.thisArg) : unmappedValues as U[]; result.push(...values); return result; }
/** The amount of values stored in the binary heap. */ get length(): number { return this.#data.length; }
/** Returns the greatest value in the binary heap, or undefined if it is empty. */ peek(): T | undefined { return this.#data[0]; }
/** Removes the greatest value from the binary heap and returns it, or null if it is empty. */ pop(): T | undefined { const size: number = this.#data.length - 1; swap(this.#data, 0, size); let parent = 0; let right: number = 2 * (parent + 1); let left: number = right - 1; while (left < size) { const greatestChild = right === size || this.compare(this.#data[left], this.#data[right]) <= 0 ? left : right; if (this.compare(this.#data[greatestChild], this.#data[parent]) < 0) { swap(this.#data, parent, greatestChild); parent = greatestChild; } else { break; } right = 2 * (parent + 1); left = right - 1; } return this.#data.pop(); }
/** Adds values to the binary heap. */ push(...values: T[]): number { for (const value of values) { let index: number = this.#data.length; let parent: number = getParentIndex(index); this.#data.push(value); while ( index !== 0 && this.compare(this.#data[index], this.#data[parent]) < 0 ) { swap(this.#data, parent, index); index = parent; parent = getParentIndex(index); } } return this.#data.length; }
/** Removes all values from the binary heap. */ clear() { this.#data = []; }
/** Checks if the binary heap is empty. */ isEmpty(): boolean { return this.#data.length === 0; }
/** Returns an iterator for retrieving and removing values from the binary heap. */ *drain(): IterableIterator<T> { while (!this.isEmpty()) { yield this.pop() as T; } }
*[Symbol.iterator](): IterableIterator<T> { yield* this.drain(); }}