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LeetCodeSharp/Problems/Solution146.cs

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+// [146] LRU Cache
+
+
+using System.Collections.Generic;
+
+namespace LeetCodeSharp.Problems146
+{
+    // Submission codes start here
+    public class LRUCache
+    {
+        private readonly int _capacity;
+        private readonly Dictionary<int, LinkedListNode<KeyValuePair<int, int>>> _map;
+        private readonly LinkedList<KeyValuePair<int, int>> _linkedList = new LinkedList<KeyValuePair<int, int>>();
+
+        public LRUCache(int capacity)
+        {
+            _map = new Dictionary<int, LinkedListNode<KeyValuePair<int, int>>>();
+            _capacity = capacity;
+        }
+
+        public int Get(int key)
+        {
+            if (!_map.TryGetValue(key, out var node))
+            {
+                return -1;
+            }
+
+            _linkedList.Remove(node);
+            var newNode = new LinkedListNode<KeyValuePair<int, int>>(node.Value);
+            _map[key] = newNode;
+            _linkedList.AddFirst(newNode);
+
+            return node.Value.Value;
+        }
+
+        public void Put(int key, int value)
+        {
+            if (_map.TryGetValue(key, out var existedNode))
+            {
+                _linkedList.Remove(existedNode);
+                _map.Remove(key);
+            }
+
+            var node = new LinkedListNode<KeyValuePair<int, int>>(new KeyValuePair<int, int>(key, value));
+            _linkedList.AddFirst(node);
+            _map.Add(key, node);
+
+            if (_map.Count > _capacity)
+            {
+                var last = _linkedList.Last;
+
+                if (last != null)
+                {
+                    _linkedList.RemoveLast();
+                    _map.Remove(last.Value.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);
+     */
+
+    // Submission codes end here
+}