Leetcode - Insert Delete GetRandom O(1)
https://leetcode.com/problems/insert-delete-getrandom-o1/
Design a data structure that supports all following operations in average O(1) time.
-
insert(val): Inserts an item val to the set if not already present. -
remove(val): Removes an item val from the set if present. -
getRandom: Returns a random element from current set of elements. Each element must have the same probability of being returned.
Example:
// Init an empty set. RandomizedSet randomSet = new RandomizedSet(); // Inserts 1 to the set. Returns true as 1 was inserted successfully. randomSet.insert(1); // Returns false as 2 does not exist in the set. randomSet.remove(2); // Inserts 2 to the set, returns true. Set now contains [1,2]. randomSet.insert(2); // getRandom should return either 1 or 2 randomly. randomSet.getRandom(); // Removes 1 from the set, returns true. Set now contains [2]. randomSet.remove(1); // 2 was already in the set, so return false. randomSet.insert(2); // Since 2 is the only number in the set, getRandom always return 2. randomSet.getRandom();
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 | import "math/rand"type RandomizedSet struct { hash map[int]int arr []int}/** Initialize your data structure here. */func Constructor() RandomizedSet { return RandomizedSet{ hash: map[int]int{}, arr: []int{}, }}/** Inserts a value to the set. Returns true if the set did not already contain the specified element. */func (this *RandomizedSet) Insert(val int) bool { if _, ok := this.hash[val]; ok { return false } this.arr = append(this.arr, val) this.hash[val] = len(this.arr)-1 return true}/** Removes a value from the set. Returns true if the set contained the specified element. */func (this *RandomizedSet) Remove(val int) bool { p, ok := this.hash[val] if !ok { return false } if p != len(this.arr)-1 { this.hash[this.arr[len(this.arr)-1]] = p this.arr[p] = this.arr[len(this.arr)-1] } this.arr = this.arr[:len(this.arr)-1] delete(this.hash, val) return true}/** Get a random element from the set. */func (this *RandomizedSet) GetRandom() int { idx := rand.Int() % len(this.arr) return this.arr[idx]}/** * Your RandomizedSet object will be instantiated and called as such: * obj := Constructor(); * param_1 := obj.Insert(val); * param_2 := obj.Remove(val); * param_3 := obj.GetRandom(); */ |
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