集合 #15

class Set<T> {
  private items: any

  constructor() {
    this.items = {}
  }

  add(element: T) {
    if (!this.has(element)) {
      this.items[element] = element
      return true
    }

    return false
  }

  has(element: T) {
    return Object.prototype.hasOwnProperty.call(this.items, element)
  }

  remove(element: T) {
    if (this.has(element)) {
      delete this.items[element]
      return true
    }
    return false
  }

  size() {
    return Object.keys(this.items).length
  }

  clear() {
    this.items = {}
  }

  values() {
    return Object.keys(this.items)
  }

  union(otherSet: Set<T>) {
    const set = new Set()

    this.values().forEach(value => set.add(value))
    otherSet.values().forEach(value => set.add(value))

    return set
  }

  interSection(otherSet: Set<T>) {
    const set = new Set()


    const values = this.values()
    const otherValues = otherSet.values()

    let biggerSet = values;
    let smallerSet = otherValues;

    if (values.length < otherValues.length) {
      smallerSet = values
      biggerSet = otherValues
    }

    smallerSet.forEach(v => {
      if (biggerSet.includes(v)) set.add(v)
    })
    return set
  }

  isSubsetOf(otherSet: Set<T>) {
    if (this.size() > otherSet.size()) {
      return false;
    }

    let isSubset = true;
    this.values().every((value: any) => {
      if (!otherSet.has(value)) {
        isSubset = false;
        return false;
      }
      return true;
    });

    return isSubset;
  }

  difference(otherSet: Set<T>) {
    const set = new Set()

    this.values().forEach((value: any) => {
      if (!otherSet.has(value)) set.add(value)
    })
    return set
  }

}