LRUCacheSetObject.swift

class LRUCache<T: Hashable, U> {
  
  // ...
  
  /// Sets the specified value at the specified key in the cache.
    func setObject(for key: T, value: U) {
        let element = CachePayload(key: key, value: value)
        let node = Node(value: element)

        if let existingNode = dictionary[key] {
            linkedList.moveToHead(node: existingNode)
            linkedList.head?.payload.value = value
            dictionary[key] = node
        } else {
            if linkedList.count == capacity {
                if let leastAccessedKey = linkedList.tail?.payload.key {
                    dictionary[leastAccessedKey] = nil
                }
                linkedList.remove()
            }

            linkedList.insert(node: node, at: 0)
            dictionary[key] = node
        }
    }
}