JS用链表实现队列，附测试代码

Posted 2021-09-25 hans774882968

我偶然查了查网上js实现队列、优先队列的代码，tmd全是直接封装数组，学前端的难道没一个会算法的？

在此提供一份队列的实现，使用链表。附测试数据，以及NC114的AC代码（注：这份代码居然跑得比用js数组做队列的要慢555）。

实现

class ListNode {
  constructor(v = -1, n = null) {
    this.val = v
    this.next = n
  }
}
class Queue {
  constructor() {
    let u = new ListNode()
    this.hd = u
    this.tl = u
    this.sz = 0
  }

  push(v) {
    let u = new ListNode(v)
    this.tl.next = u
    this.tl = u
    this.sz++
  }

  pop() {
    if (!this.sz) return
    this.hd = this.hd.next
    this.sz--
  }

  front() {
    if (!this.sz) return
    return this.hd.next.val
  }

  size() {
    return this.sz
  }

  empty() {
    return this.sz <= 0
  }
}

测试

let q = new Queue()
console.log(q.front(),q.size(),q.empty())//undefined 0 t
q.push(10)
console.log(q.front(),q.size(),q.empty())//10 1 f
q.push('wsw')
console.log(q.front(),q.size(),q.empty())//10 2 f
q.pop()
console.log(q.front(),q.size(),q.empty())//'wsw' 1 f
q.pop()
console.log(q.front(),q.size(),q.empty())//undefined 0 t
q.pop()
console.log(q.front(),q.size(),q.empty())//undefined 0 t

q.push(18)
console.log(q.front(),q.size(),q.empty())//18 1 f
for (let i = 19; i < 30; ++i) q.push(i)
for (let i = 19; i <= 31; ++i) {
  q.pop()
  console.log(q.front(), q.size(), q.empty())//19~29及两个undefined
}
q.push(114514)
console.log(q.front(), q.size(), q.empty())//114514 1 f

NC114

"use strict";

class ListNode {
  constructor(v = -1, n = null) {
    this.val = v
    this.next = n
  }
}
class Queue {
  constructor() {
    let u = new ListNode()
    this.hd = u
    this.tl = u
    this.sz = 0
  }

  push(v) {
    let u = new ListNode(v)
    this.tl.next = u
    this.tl = u
    this.sz++
  }

  pop() {
    if (!this.sz) return
    this.hd = this.hd.next
    this.sz--
  }

  front() {
    if (!this.sz) return
    return this.hd.next.val
  }

  size() {
    return this.sz
  }

  empty() {
    return this.sz <= 0
  }
}

function Print(pRoot) {
  // write code here
  let q = new Queue()
  if (pRoot) q.push(pRoot)
  let ans = []
  for (let dis = 0; !q.empty(); ++dis) {
    let sz = q.size()
    let cur = []
    while (sz--) {
      const u = q.front()
      q.pop()
      cur.push(u.val)
      if (u.left) q.push(u.left)
      if (u.right) q.push(u.right)
    }
    ans.push(dis % 2 ? cur.reverse() : cur)
  }
  return ans
}
module.exports = {
  Print : Print
};