Add C++ implementation

Signed-off-by: begeekmyfriend <[email protected]>

Author: begeekmyfriend

146_lru_cache/lru_cache.cc

@@ -0,0 +1,50 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+/**
+ * Your LRUCache object will be instantiated and called as such:
+ * LRUCache* obj = new LRUCache(capacity);
+ * int param_1 = obj->get(key);
+ * obj->put(key,value);
+ */
+class LRUCache {
+public:
+    LRUCache(int capacity) {
+        capacity_ = capacity;
+    }
+
+    int get(int key) {
+        if (ht_.find(key) == ht_.end()) {
+            return -1;
+        }
+
+        int value = ht_[key]->second;
+        if (li_.front().second != value) {
+            li_.erase(ht_[key]);
+            li_.push_front(make_pair(key, value));
+            ht_[key] = li_.begin(); // iterator failure
+        }
+
+        return value;
+    }
+
+    void put(int key, int value) {
+        if (ht_.find(key) != ht_.end()) {
+            li_.erase(ht_[key]);
+        } else {
+            if (li_.size() == capacity_) {
+                auto lru = li_.back();
+                li_.pop_back();
+                ht_.erase(lru.first);
+            }
+        }
+        li_.push_front(make_pair(key, value));
+        ht_[key] = li_.begin(); // iterator failure
+    }
+
+private:
+    int capacity_;
+    list<pair<int, int>> li_;
+    unordered_map<int, pair<int, int>::iterator> ht_;
+};