Merge pull request #2 from Abhishek21sh/master

LRU Cache Implementation

LRU Cache Implementation

@@ -0,0 +1,73 @@
+#include <bits/stdc++.h> 
+using namespace std; 
+
+class LRUCache 
+{ 
+    // store keys of cache 
+    list<int> dq; 
+
+    // store references of key in cache 
+    unordered_map<int, list<int>::iterator> ma; 
+    int csize; //maximum capacity of cache 
+
+public: 
+    LRUCache(int); 
+    void refer(int); 
+    void display(); 
+}; 
+
+LRUCache::LRUCache(int n) 
+{ 
+    csize = n; 
+} 
+
+/* Refers key x with in the LRU cache */
+void LRUCache::refer(int x) 
+{ 
+    // not present in cache 
+    if (ma.find(x) == ma.end()) 
+    { 
+        // cache is full 
+        if (dq.size() == csize) 
+        { 
+            //delete least recently used element 
+            int last = dq.back(); 
+            dq.pop_back(); 
+            ma.erase(last); 
+        } 
+    } 
+
+    // present in cache 
+    else
+        dq.erase(ma[x]); 
+
+    // update reference 
+    dq.push_front(x); 
+    ma[x] = dq.begin(); 
+} 
+
+// display contents of cache 
+void LRUCache::display() 
+{ 
+    for (auto it = dq.begin(); it != dq.end(); 
+                                        it++) 
+        cout << (*it) << " "; 
+
+    cout << endl; 
+} 
+
+// Driver program to test above functions 
+int main() 
+{ 
+    LRUCache ca(4); 
+
+    ca.refer(1); 
+    ca.refer(2); 
+    ca.refer(3); 
+    ca.refer(1); 
+    ca.refer(4); 
+    ca.refer(5); 
+    ca.display(); 
+
+    return 0; 
+}