abstractclassespolymorphism added

C++/abstractclassespolymorphism.cpp

@@ -0,0 +1,118 @@
+// Abstract Classes - Polymorphism in C++
+#include <iostream>
+#include <vector>
+#include <map>
+#include <string>
+#include <algorithm>
+#include <set>
+#include <cassert>
+using namespace std;
+
+struct Node{
+   Node* next;
+   Node* prev;
+   int value;
+   int key;
+   Node(Node* p, Node* n, int k, int val):prev(p),next(n),key(k),value(val){};
+   Node(int k, int val):prev(NULL),next(NULL),key(k),value(val){};
+};
+
+class Cache{
+
+   protected: 
+   map<int,Node*> mp; //map the key to the node in the linked list
+   int cp;  //capacity
+   Node* tail; // double linked list tail pointer
+   Node* head; // double linked list head pointer
+   virtual void set(int, int) = 0; //set function
+   virtual int get(int) = 0; //get function
+
+};
+
+
+
+class LRUCache: public Cache
+{
+public:
+    LRUCache(int c)
+    {
+      cp = c;
+    }
+    void set(int k, int v)
+    {
+
+     Node* N;
+        if ( mp.empty() )
+        {
+            N = new Node(k,v);
+            tail = head = N;
+            mp[k] = N;
+            return;
+        }
+        auto it = mp.find(k);
+        if ( it != mp.end() )
+        {
+            it->second->value = v;
+            if ( head == it->second )
+            {
+                return;
+            }
+            it->second->prev->next = it->second->next;
+            if ( tail == it->second )
+            {
+                tail = tail->prev;
+            }
+            else
+            {
+                it->second->next->prev = it->second->prev;
+            }
+            it->second->next = head;
+            it->second->prev = nullptr;
+            head->prev = it->second;
+            head = it->second;
+        }
+        else
+        {
+            N = new Node(head->prev, head, k, v);
+            head->prev = N;
+            head = N;
+            mp[k] = N;
+            if ( mp.size() > cp )
+            {
+                tail = tail->prev;
+                mp.erase(tail->next->key);
+                delete tail->next;
+                tail->next = nullptr;
+            }
+        }
+    }
+    int get(int k)
+    {
+        auto it = mp.find(k);
+        if ( it != mp.end() )
+        {
+            return it->second->value;
+        }
+        return -1;
+    }
+};
+ int main() {
+   int n, capacity,i;
+   cin >> n >> capacity;
+   LRUCache l(capacity);
+   for(i=0;i<n;i++) {
+      string command;
+      cin >> command;
+      if(command == "get") {
+         int key;
+         cin >> key;
+         cout << l.get(key) << endl;
+      } 
+      else if(command == "set") {
+         int key, value;
+         cin >> key >> value;
+         l.set(key,value);
+      }
+   }
+   return 0;
+}