380. Insert Delete GetRandom O(1)

1class RandomizedSet {
2    map: Map<number, number>;
3    arr: number[]
4
5    constructor() {
6        this.map = new Map();
7        this.arr = []
8    }
9
10    insert(val: number): boolean {
11        if (this.map.has(val)) return false;
12        this.map.set(val, this.arr.length);
13        this.arr.push(val);
14        return true
15    }
16
17    remove(val: number): boolean {
18        if (!this.map.has(val)) return false
19        const idx = this.map.get(val);
20        const last = this.arr.at(-1);
21        this.map.set(last, idx)
22
23        this.arr[idx] = last;
24        this.arr.pop();
25        this.map.delete(val)
26        return true
27    }
28
29    getRandom(): number {
30        const idx = Math.floor(Math.random() * this.arr.length)
31        return this.arr[idx];
32    }
33}
34
35/**
36 * Your RandomizedSet object will be instantiated and called as such:
37 * var obj = new RandomizedSet()
38 * var param_1 = obj.insert(val)
39 * var param_2 = obj.remove(val)
40 * var param_3 = obj.getRandom()
41 */