Create LRU_Cache.cpp

LeetCode/LRU_Cache.cpp

@@ -0,0 +1,80 @@
+struct Node {
+    int key, value;
+    Node *prev, *next;
+    Node(int key, int value) {
+        this->key=key;
+        this->value=value;
+        prev=next=nullptr;
+    }
+};
+
+class LRUCache {
+    Node *data[10001];
+    int capacity;
+    Node *head, *tail; 
+public:
+
+    LRUCache(int capacity) {
+        for(int i=0; i<10001; i++)
+            data[i]=nullptr;
+        this->capacity=capacity;
+        head=new Node(-1,-1); // dummy nodes
+        tail=new Node(-1,-1);
+        head->next=tail;
+        tail->prev=head;
+    }
+
+    int get(int key) {
+        if(data[key]!=nullptr)
+        {
+            Node *temp=data[key];
+            Node *node=new Node(temp->key,temp->value);
+            node->next=head->next;
+            head->next=node;
+            node->prev=head;
+            node->next->prev=node;
+            data[key]=node;
+
+            temp->prev->next=temp->next;
+            temp->next->prev=temp->prev;
+            delete temp;
+            return node->value;
+        }
+        else
+            return -1;
+    }
+
+    void put(int key, int value) {
+        if(data[key]!=nullptr)
+        {
+            Node *temp=data[key];
+            Node *node=new Node(key,value);
+            node->next=head->next;
+            head->next=node;
+            node->prev=head;
+            node->next->prev=node;
+            data[key]=node;
+
+            temp->prev->next=temp->next;
+            temp->next->prev=temp->prev;
+            delete temp;
+            return;
+        }
+        capacity--;
+        if(capacity<0)
+        {
+            Node *node=tail->prev;
+            node->prev->next=node->next;
+            node->next->prev=node->prev;
+            data[node->key]=nullptr;
+            delete node;
+            capacity=0;
+        }
+        Node *node=new Node(key,value);
+        node->next=head->next;
+        head->next=node;
+        node->prev=head;
+        node->next->prev=node;
+        data[key]=node;
+    }
+};