S 12345 add new ds lru cache

src/main/java/com/williamfiset/algorithms/datastructures/cache/LRUCache.java

@@ -0,0 +1,89 @@
+package com.williamfiset.algorithms.datastructures.cache;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class LRUCache<K,V>{
+
+    private final Map<K, Node<K,V>> map = new HashMap<>();
+    private final Node<K,V> head;
+    private final Node<K,V> last;
+    private final int capacity;
+
+    public LRUCache(int capacity){
+        this.capacity = capacity;
+        head = new Node<>(null,null);
+        last = new Node<>(null,null);
+        head.next = last;
+        last.prev = head;
+    }
+
+    public V get(K key){
+        Node<K,V> node = map.get(key);
+        if (node == null){
+            return null;
+        }
+        remove(node);
+        insert(node);
+        return node.value;
+    }
+
+
+    public void put(K key, V value) {
+        if (map.containsKey(key)) {
+            remove(map.get(key));
+        }
+        if (map.size() == capacity) {
+            remove(last.prev);
+        }
+        insert(new Node<>(key, value));
+    }
+
+    private void insert(Node<K,V> node) {
+        map.put(node.key, node);
+        node.next = head.next;
+        head.next.prev = node;
+        node.prev = head;
+        head.next = node;
+    }
+
+    private void remove(Node<K,V> node) {
+        map.remove(node.key);
+        node.prev.next = node.next;
+        node.next.prev = node.prev;
+    }
+
+
+    private static class Node<K,V>{
+        K key;
+        V value;
+        Node<K,V> prev;
+        Node<K,V> next;
+
+        public Node(K key, V value){
+            this.key = key;
+            this.value = value;
+        }
+    }
+
+    @Override
+    public String toString() {
+        return "LRUCache{" +
+                 map.keySet() +
+                '}';
+    }
+
+    public static void main(String[] args) {
+        LRUCache<Integer,Integer> lruCache = new LRUCache<>(3);
+        lruCache.put(1,1);
+        lruCache.put(2,2);
+        lruCache.put(3,3);
+
+        lruCache.put(4,4);
+
+        //should print 2,3,4
+        System.out.println(lruCache);
+
+    }
+
+}