problem0380

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380. Insert Delete GetRandom O(1)

题目

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();

解题思路

见程序注释

Documentation

Index

• type RandomizedSet
  • func Constructor() RandomizedSet
  • func (r *RandomizedSet) GetRandom() int
  • func (r *RandomizedSet) Insert(val int) bool
  • func (r *RandomizedSet) Remove(val int) bool

Types

type RandomizedSet

type RandomizedSet struct {
	// contains filtered or unexported fields
}

RandomizedSet 是一个随机获取的集合

func Constructor

func Constructor() RandomizedSet

Constructor returns RandomizedSet * Initialize your data structure here.

func (*RandomizedSet) GetRandom

func (r *RandomizedSet) GetRandom() int

GetRandom 获取随机数据 * Get a random element from the set.

func (*RandomizedSet) Insert

func (r *RandomizedSet) Insert(val int) bool

Insert 插入数据 * Inserts a value to the set. Returns true if the set did not already contain the specified element.

func (*RandomizedSet) Remove

func (r *RandomizedSet) Remove(val int) bool

Remove 删除数据 * Removes a value from the set. Returns true if the set contained the specified element.