优先队列，默认大顶堆

PriorityQueue.js

class PriorityQueue {
    constructor(data = [], compare = defaultCompare) {
        this.data = data
        this.length = this.data.length
        this.compare = compare

        if (this.length > 0) {
            for (let i = (this.length >> 1) - 1; i >= 0; i--) this._down(i)
        }
    }

    enQueue(item) {
        this.data.push(item)
        this.length ++
        this._up(this.length - 1)
    }

    deQueue() {
        if (this.length === 0) return undefined

        const top = this.data[0]
        const bottom = this.data.pop()
        
        this.length --

        if (this.length > 0) {
            this.data[0] = bottom
            this._down(0)
        }

        return top
    }

    _up(pos) {
        const {data, compare} = this
        const item = data[pos]

        while (pos > 0) {
            const parent = (pos - 1) >> 1
            const current = data[parent]
            if (compare(item, current) >= 0) break
            data[pos] = current
            pos = parent
        }

        data[pos] = item
    }

    _down(pos) {
        const {data, compare} = this
        const halfLength = this.length >> 1
        const item = data[pos]

        while (pos < halfLength) {
            let left = (pos << 1) + 1
            let best = data[left]
            const right = left + 1

            if (right < this.length && compare(data[right], best) < 0) {
                left = right
                best = data[right]
            }
            
            if (compare(best, item) >= 0) break

            data[pos] = best
            pos = left
        }

        data[pos] = item
    }
}

function defaultCompare(a, b) {
    return a < b ? -1 : a > b ? 1 : 0;
}