leetcode

0 class RandomizedSet {

1 public:

2 RandomizedSet() {}

3

4 bool insert(int val) {

5 if (um.count(val)) return false;

6 nums.emplace_back(val);

7 um[val] = nums.size() - 1;

8 return true;

9 }

10

11 bool remove(int val) {

12 if (!um.count(val)) return false;

13 int last = nums.back();

14 um[last] = um[val];

15 nums[um[val]] = last;

16 nums.pop_back();

17 um.erase(val);

18 return true;

19 }

20

21 int getRandom() { return nums[rand() % nums.size()]; }

22

23 private:

24 vector<int> nums;

25 unordered_map<int, int> um;

26 };