380. Insert Delete GetRandom O(1)

1class RandomizedSet {
2    private list: number[];
3    private hashmap: Map<number, number>; // {val: list.length}
4
5    constructor() {
6        this.list = [];
7        this.hashmap = new Map();
8    }
9
10    insert(val: number): boolean {
11        if (this.hashmap.has(val)) {
12            return false
13        }
14        this.list.push(val);
15        this.hashmap.set(val, this.list.length - 1);
16        return true;
17    }
18
19    remove(val: number): boolean {
20        if (!this.hashmap.has(val)) {
21            return false;
22        }
23
24        let index = this.hashmap.get(val)!;
25        const lastValue = this.list[this.list.length - 1];
26
27        this.list[index] = lastValue;
28        this.hashmap.set(lastValue, index);
29
30        this.hashmap.delete(val);
31        this.list.pop();
32        
33        return true;
34    }
35
36    getRandom(): number {
37        const randomInt = Math.floor(Math.random() * this.list.length);
38        return this.list[randomInt];
39    }
40}
41
42/**
43 * Your RandomizedSet object will be instantiated and called as such:
44 * var obj = new RandomizedSet()
45 * var param_1 = obj.insert(val)
46 * var param_2 = obj.remove(val)
47 * var param_3 = obj.getRandom()
48 */