[leetCode/JS] 380. Insert Delete GetRandom O(1)

난이도 [ 🤔 ] Medium

문제 설명

Implement the RandomizedSet class:

• RandomizedSet() Initializes the RandomizedSet object.
• bool insert(int val) Inserts an item val into the set if not present. Returns true if the item was not present, false otherwise.
• bool remove(int val) Removes an item val from the set if present. Returns true if the item was present, false otherwise.
• int getRandom() Returns a random element from the current set of elements (it's guaranteed that at least one element exists when this method is called). Each element must have the same probability of being returned.

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

 

RandomizedSet 클래스를 만들어서 
insert(val) 로 value를 넣고, remove()로 지우고, getRandom() 랜덤 1개 뽑아온다.

 

 

입출력 예

Example 1:

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

• -231 <= val <= 231 - 1
• At most 2 * 105 calls will be made to insert, remove, and getRandom.
• There will be at least one element in the data structure when getRandom is called.

 

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내 솔루션

• 왜 Medium 이지.. 싶은 문제다. 
• array로 해볼까 하다가 그냥 Set이 지우기 쉬워서 해봤다.
• 대신 좀 느린 것 같다.

class RandomizedSet {
  constructor() {
    this.nums = new Set();
  }
  insert(val) {
    if(this.nums.has(val)) {
      return false;
    }
    this.nums.add(val);
    return true;
  }
  remove(val) {
    if(this.nums.has(val)) {
      this.nums.delete(val)
      return true;
    }
    return false;
  }
  getRandom() {
    return [...this.nums][Math.floor(Math.random() * this.nums.size)]
  }
}

 

감상평

• 쉬웠다! 오랜만에 쉽고 재미있는 가벼운 문제