手写常用数据结构（JS）

// 运行环境：Node.js 14+（需支持私有字段 #）
// 保存为 dsa-l7.js，执行：node dsa-l7.js

class Stack {
  #items = []
  push(x) { this.#items.push(x) }
  pop() { return this.#items.pop() }
  peek() { return this.#items[this.#items.length - 1] }
  get size() { return this.#items.length }
  isEmpty() { return this.size === 0 }
}

class Queue {
  #items = []
  #head = 0
  enqueue(x) { this.#items.push(x) }
  dequeue() { return this.#head < this.#items.length ? this.#items[this.#head++] : undefined }
  peek() { return this.#items[this.#head] }
  get size() { return this.#items.length - this.#head }
  isEmpty() { return this.size === 0 }
}

class MinHeap {
  #h = []
  push(x) { this.#h.push(x); this.#siftUp(this.#h.length - 1) }
  pop() {
    if (!this.#h.length) return undefined
    const top = this.#h[0]
    const last = this.#h.pop()
    if (this.#h.length) { this.#h[0] = last; this.#siftDown(0) }
    return top
  }
  peek() { return this.#h[0] }
  get size() { return this.#h.length }
  #siftUp(i) {
    while (i > 0) {
      const p = (i - 1) >> 1
      if (this.#h[p] <= this.#h[i]) break
      ;[this.#h[p], this.#h[i]] = [this.#h[i], this.#h[p]]
      i = p
    }
  }
  #siftDown(i) {
    const n = this.#h.length
    while (true) {
      let m = i, l = 2 * i + 1, r = 2 * i + 2
      if (l < n && this.#h[l] < this.#h[m]) m = l
      if (r < n && this.#h[r] < this.#h[m]) m = r
      if (m === i) break
      ;[this.#h[m], this.#h[i]] = [this.#h[i], this.#h[m]]
      i = m
    }
  }
}

// 调用示例
const s = new Stack(); s.push(1); s.push(2); console.log(s.pop()) // 2
const h = new MinHeap(); [5, 3, 8, 1].forEach(x => h.push(x))
console.log(h.pop(), h.pop(), h.pop()) // 1 3 5（最小优先出队）