leetcode randset

randset.js

class RandomizedSet {
  constructor() {
    this.set = new Map();
    this.array = [];
  }

  insert(val) {
    if (this.set.has(val)) {
      return false;
    }
    this.array.push(val);
    this.set.set(val, this.array.length - 1);
    return true;
  }

  remove(val) {
    if (!this.set.has(val)) {
      return false;
    }

    const indexToRemove = this.set.get(val);
    const lastIndex = this.array.length - 1;

    [this.array[indexToRemove], this.array[lastIndex]] = [this.array[lastIndex], this.array[indexToRemove]];
    this.set.set(this.array[indexToRemove], indexToRemove);

    this.array.pop();
    this.set.delete(val);

    return true;
  }

  getRandom() {
    const randomIndex = Math.floor(Math.random() * this.array.length);
    return this.array[randomIndex];
  }
}