---
title: '380. Insert Delete GetRandom O(1)'
description: 'Implement the RandomizedSet class:'
icon: dot
topics:
  - { name: "Array", slug: "array" }
  - { name: "Hash Table", slug: "hash-table" }
  - { name: "Math", slug: "math" }
  - { name: "Design", slug: "design" }
  - { name: "Randomized", slug: "randomized" }
issue: "https://github.com/prdlk/leetcode/issues/90"
sidebar:
  label: 'Insert Delete GetRandom O(1)'
  badge: 'Medium'
---

::::warning
You must implement the functions of the class such that each function works in average O(1) time complexity.
::::

### Example 1:
- Input: ``
- Output: ``
- Explanation: Input ["RandomizedSet", "insert", "remove", "insert", "getRandom", "remove", "insert", "getRandom"] `[[]`, `[1]`, `[2]`, `[2]`, `[]`, `[1]`, `[2]`, []] Output [null, true, false, true, `2`, true, false, 2] Explanation RandomizedSet randomizedSet = new RandomizedSet(); randomizedSet.insert(1); // Inserts `1` to the set. Returns true as `1` was inserted successfully. randomizedSet.remove(2); // Returns false as `2` does not exist in the set. randomizedSet.insert(2); // Inserts `2` to the set, returns true. Set now contains `[1,2]`. randomizedSet.getRandom(); // getRandom() should return either `1` or `2` randomly. randomizedSet.remove(1); // Removes `1` from the set, returns true. Set now contains `[2]`. randomizedSet.insert(2); // `2` was already in the set, so return false. randomizedSet.getRandom(); // Since `2` is the only number in the set, getRandom() will always return `2`.

### Constraints:

- `-2^31 <= val <= 2^31 - 1`
- At most 2 * 10^5 calls will be made to insert, remove, and getRandom.
- There will be at least one element in the data structure when getRandom is called.

## Solution

```py
from random import choice


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

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

    def remove(self, val: int) -> bool:
        if val in self.dict:
            last, idx = self.list[-1], self.dict[val]
            self.list[idx], self.dict[last] = last, idx
            self.list.pop()
            del self.dict[val]
            return True
        return False

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


# Your RandomizedSet object will be instantiated and called as such:
# obj = RandomizedSet()
# param_1 = obj.insert(val)
# param_2 = obj.remove(val)
# param_3 = obj.getRandom()
```