Insert Delete GetRandom O(1)

class RandomizedSet {
    vector<int> vals;
    unordered_map<int,int> pos;
public:
    bool insert(int val) {
        if (pos.count(val)) return false;
        pos[val] = vals.size();
        vals.push_back(val);
        return true;
    }
    bool remove(int val) {
        auto it = pos.find(val);
        if (it == pos.end()) return false;
        int idx = it->second, last = vals.back();
        vals[idx] = last;
        pos[last] = idx;
        vals.pop_back();
        pos.erase(it);
        return true;
    }
    int getRandom() {
        return vals[rand() % vals.size()];
    }
};

import "math/rand"

type RandomizedSet struct {
    vals []int
    pos  map[int]int
}

func Constructor() RandomizedSet {
    return RandomizedSet{pos: map[int]int{}}
}

func (s *RandomizedSet) Insert(val int) bool {
    if _, ok := s.pos[val]; ok {
        return false
    }
    s.pos[val] = len(s.vals)
    s.vals = append(s.vals, val)
    return true
}

func (s *RandomizedSet) Remove(val int) bool {
    idx, ok := s.pos[val]
    if !ok {
        return false
    }
    last := s.vals[len(s.vals)-1]
    s.vals[idx] = last
    s.pos[last] = idx
    s.vals = s.vals[:len(s.vals)-1]
    delete(s.pos, val)
    return true
}

func (s *RandomizedSet) GetRandom() int {
    return s.vals[rand.Intn(len(s.vals))]
}

import random

class RandomizedSet:
    def __init__(self):
        self.vals: list = []
        self.pos: dict = {}

    def insert(self, val: int) -> bool:
        if val in self.pos:
            return False
        self.pos[val] = len(self.vals)
        self.vals.append(val)
        return True

    def remove(self, val: int) -> bool:
        if val not in self.pos:
            return False
        idx = self.pos[val]
        last = self.vals[-1]
        self.vals[idx] = last
        self.pos[last] = idx
        self.vals.pop()
        del self.pos[val]
        return True

    def getRandom(self) -> int:
        return random.choice(self.vals)

class RandomizedSet {
    constructor() {
        this.vals = [];
        this.pos = new Map();
    }

    insert(val) {
        if (this.pos.has(val)) return false;
        this.pos.set(val, this.vals.length);
        this.vals.push(val);
        return true;
    }

    remove(val) {
        if (!this.pos.has(val)) return false;
        const idx = this.pos.get(val);
        const last = this.vals[this.vals.length - 1];
        this.vals[idx] = last;
        this.pos.set(last, idx);
        this.vals.pop();
        this.pos.delete(val);
        return true;
    }

    getRandom() {
        return this.vals[Math.floor(Math.random() * this.vals.length)];
    }
}

class RandomizedSet {
    private List<Integer> vals = new ArrayList<>();
    private Map<Integer, Integer> pos = new HashMap<>();
    private Random rng = new Random();

    public boolean insert(int val) {
        if (pos.containsKey(val)) return false;
        pos.put(val, vals.size());
        vals.add(val);
        return true;
    }

    public boolean remove(int val) {
        Integer idx = pos.get(val);
        if (idx == null) return false;
        int last = vals.get(vals.size() - 1);
        vals.set(idx, last);
        pos.put(last, idx);
        vals.remove(vals.size() - 1);
        pos.remove(val);
        return true;
    }

    public int getRandom() {
        return vals.get(rng.nextInt(vals.size()));
    }
}

class RandomizedSet {
    private vals: number[] = [];
    private pos: Map<number, number> = new Map();

    insert(val: number): boolean {
        if (this.pos.has(val)) return false;
        this.pos.set(val, this.vals.length);
        this.vals.push(val);
        return true;
    }

    remove(val: number): boolean {
        if (!this.pos.has(val)) return false;
        const idx = this.pos.get(val)!;
        const last = this.vals[this.vals.length - 1];
        this.vals[idx] = last;
        this.pos.set(last, idx);
        this.vals.pop();
        this.pos.delete(val);
        return true;
    }

    getRandom(): number {
        return this.vals[Math.floor(Math.random() * this.vals.length)];
    }
}