HashTableValueOps.swift

struct HashTable<Key: Hashable, Value> {
  
  // Code added earlier
  
    @discardableResult
    mutating func updateValue(_ value: Value, forKey key: Key) -> Value? {
        var itemIndex: Int
        itemIndex = self.index(for: key)
        for (i, element) in buckets[itemIndex].enumerated() {
            if element.key == key {
                let oldValue = element.value
                buckets[itemIndex][i].value = value
                return oldValue
            }
        }
        buckets[itemIndex].append(HashElement(key: key, value: value))
        return nil
    }
    
    @discardableResult
    mutating func removeValue(for key: Key) -> Value? {
        let index = self.index(for: key)
        for (i, element) in buckets[index].enumerated() {
            if element.key == key {
                buckets[index].remove(at: i)
                return element.value
            }
        }
        return nil
    }
}