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LRUCache.cs
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LRUCache.cs
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using System;
using System.Collections.Generic;
namespace LRUCache
{
public class LRUCache
{
private int _capacity;
private Dictionary<int, LinkedNode> lruDictionary;
private LinkedNode first, last;
public LRUCache(int capacity)
{
if (capacity <= 0)
{
throw new ArgumentOutOfRangeException("Capacity cannot be zero or negative.");
}
_capacity = capacity;
lruDictionary = new Dictionary<int, LinkedNode>();
}
public int Get(int key)
{
LinkedNode nodeToGet;
if (!lruDictionary.TryGetValue(key, out nodeToGet))
{
return -1;
}
removeNode(nodeToGet);
addAtTop(nodeToGet);
return nodeToGet.Value;
}
public void Put(int key, int value)
{
// Input sanitization
if (key <= 0)
{
throw new ArgumentOutOfRangeException("Key cannot be zero or negative.");
}
if (value < 0)
{
throw new ArgumentOutOfRangeException("Value cannot be negative.");
}
LinkedNode newNode = new LinkedNode(key, value);
// Do work
if (lruDictionary.Count == _capacity)
{
lruDictionary.Remove(last.Key);
removeNode(last);
addAtTop(newNode);
}
else
{
addAtTop(newNode);
}
lruDictionary.Add(newNode.Key, newNode);
}
private void addAtTop(LinkedNode nodeToAdd)
{
nodeToAdd.right = first;
nodeToAdd.left = null;
if (first != null)
{
first.left = nodeToAdd;
}
first = nodeToAdd;
if (last == null)
{
last = first;
}
}
private void removeNode(LinkedNode nodeToRemove)
{
if (nodeToRemove.left != null)
{
nodeToRemove.left.right = nodeToRemove.right;
}
else
{
first = nodeToRemove.right;
}
if (nodeToRemove.right != null)
{
nodeToRemove.right.left = nodeToRemove.left;
}
else
{
last = nodeToRemove.left;
}
}
}
class LinkedNode
{
public LinkedNode(int key, int value)
{
Key = key;
Value = value;
}
public int Key { get; private set; }
public int Value { get; private set; }
public LinkedNode left { get; set; }
public LinkedNode right { get; set; }
}
}