0380-insert-delete-getrandom-o1.adoc

380. Insert Delete GetRandom O(1)

{leetcode}/problems/insert-delete-getrandom-o1/[LeetCode - Insert Delete GetRandom O(1)^]

Design a data structure that supports all following operations in average O(1) time.

1. insert(val): Inserts an item val to the set if not already present.

2. remove(val): Removes an item val from the set if present.

3. 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();

思路分析

link:{sourcedir}/_0380_InsertDeleteGetRandomO1.java[role=include]

link:{sourcedir}/_0380_InsertDeleteGetRandomO1_2.java[role=include]

参考资料

1. 380. O(1) 时间插入、删除和获取随机元素 - 官方题解

2. 380. O(1) 时间插入、删除和获取随机元素 - 【宫水三叶】数据结构运用题