Create LRU-cache(Doubly-linked-list).cpp

issue solved OpenGenus#6703

LRU-cache(Doubly-linked-list).cpp

@@ -0,0 +1,73 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+class Node {
+public:
+    int key;
+    int value;
+    Node *next;
+    Node *prev;
+
+    Node(int k, int v) : key(k), value(v) {
+        next = nullptr;
+        prev = nullptr;
+    }
+};
+
+class LRUCache {
+public:
+    int capacity;
+    unordered_map<int, Node*> mp; // map the key to the node in the linked list
+    Node *head;
+    Node *tail;
+
+    LRUCache(int c) : capacity(c) {
+        head = new Node(0, 0);
+        tail = new Node(0, 0);
+        head->next = tail;
+        tail->prev = head;
+        head->prev = nullptr;
+        tail->next = nullptr;
+    }
+
+    void addNode(Node *node) {
+        node->next = head->next;
+        head->next->prev = node;
+        node->prev = head;
+        head->next = node;
+    }
+
+    void removeNode(Node *node) {
+        node->prev->next = node->next;
+        node->next->prev = node->prev;
+    }
+
+    void moveToHead(Node *node) {
+        removeNode(node);
+        addNode(node);
+    }
+
+    int get(int key) {
+        if (mp.find(key) == mp.end())
+            return -1;
+        Node *node = mp[key];
+        moveToHead(node);
+        return node->value;
+    }
+
+    void put(int key, int value) {
+        if (mp.find(key) != mp.end()) {
+            Node *node = mp[key];
+            node->value = value;
+            moveToHead(node);
+        } else {
+            if (mp.size() == capacity) {
+                mp.erase(tail->prev->key);
+                removeNode(tail->prev);
+            }
+            Node *node = new Node(key, value);
+            addNode(node);
+            mp[key] = node;
+        }
+    }
+};