leetcode-380-insert-delete-getrandom-o1.swift

/**

Copyright (c) 2020 David Seek, LLC

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OR OTHER DEALINGS IN THE SOFTWARE.





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();

*/

/**
Big O Annotation
All operations are O(1) in time complexity.
Space complexity O(n) where n is the amount of elements in data.
*/
class RandomizedSet {
    
    private var data: Set<Int> = []

    /** Initialize your data structure here. */
    init() { }
    
    /** Inserts a value to the set. Returns true if the set did not already contain the specified element. */
    func insert(_ val: Int) -> Bool {
        
        if data.contains(val) {
            return false
        }
        data.insert(val)
        return true
    }
    
    /** Removes a value from the set. Returns true if the set contained the specified element. */
    func remove(_ val: Int) -> Bool {
        
        if !data.contains(val) {
            return false
        }
        data.remove(val)
        return true
    }
    
    /** Get a random element from the set. */
    func getRandom() -> Int {
        return data.randomElement() ?? 0
    }
}

/**
 * Your RandomizedSet object will be instantiated and called as such:
 * let obj = RandomizedSet()
 * let ret_1: Bool = obj.insert(val)
 * let ret_2: Bool = obj.remove(val)
 * let ret_3: Int = obj.getRandom()
 */