Create 146-LRU-Cache.cs

File(s) Modified: 146-LRU-Cache.cs
Language(s) Used: csharp
Submission URL: https://leetcode.com/submissions/detail/773840490/

Author: ShrujanKotturi

Diff for: csharp/146-LRU-Cache.cs

@@ -0,0 +1,98 @@
+public class Node
+{
+    public int val;
+    public int key;
+    public Node prev;
+    public Node next;
+
+    public Node(int key, int val)
+    {
+        this.key = key;
+        this.val = val;
+        prev = null;
+        next = null;
+    }
+}
+
+public class LRUCache
+{
+    private Dictionary<int, Node> keyValue = new();
+    private int _capacity;
+    private Node left;
+    private Node right;
+
+    //T: O(1), S: O(Capacity)
+    public LRUCache(int capacity)
+    {
+        _capacity = capacity;
+        left = new Node(0, 0);
+        right = new Node(0, 0);
+        // left : LRU, right : MRU (Most recently used)
+        left.next = right;
+        right.prev = left;
+    }
+
+    //Remove from list
+    private void remove(Node node)
+    {
+        var prev = node.prev;
+        var next = node.next;
+
+        prev.next = next;
+        next.prev = prev;
+    }
+
+    // Insert at right
+    private void insert(Node node)
+    {
+        var next = right;
+        var prev = right.prev;
+
+        node.next = next;
+        next.prev = node;
+        prev.next = node;
+        node.prev = prev;
+
+    }
+
+    public int Get(int key)
+    {
+        if (!keyValue.ContainsKey(key))
+            return -1;
+        // we need to update this to be MRU
+        var node = keyValue[key];
+        remove(node);
+        insert(node);
+        return node.val;
+    }
+
+    public void Put(int key, int value)
+    {
+        if (keyValue.ContainsKey(key))
+        {
+            var node = keyValue[key];
+            keyValue.Remove(key);
+            remove(node);
+        }
+
+        var newNode = new Node(key, value);
+        keyValue.Add(key, newNode);
+        insert(newNode);
+
+        if (keyValue.Count > _capacity)
+        {
+            // remove  from the list and delete the LRU from dictionary
+            var lru = left.next;
+            remove(lru);
+            keyValue.Remove(lru.key);
+        }
+
+    }
+}
+
+/**
+ * Your LRUCache object will be instantiated and called as such:
+ * LRUCache obj = new LRUCache(capacity);
+ * int param_1 = obj.Get(key);
+ * obj.Put(key,value);
+ */