Create time-based-key-value-store.cpp

Author: kamyu104

C++/time-based-key-value-store.cpp

@@ -0,0 +1,40 @@
+// Time:  set: O(1)
+//        get: O(logn)
+// Space: O(n)
+
+class TimeMap {
+public:
+    /** Initialize your data structure here. */
+    TimeMap() {
+        
+    }
+    
+    void set(string key, string value, int timestamp) {
+        lookup_[key].emplace_back(timestamp, value);
+    }
+    
+    string get(string key, int timestamp) {
+        if (!lookup_.count(key)) {
+            return "";
+        }
+        auto it = upper_bound(lookup_[key].cbegin(),
+                              lookup_[key].cend(),
+                              make_pair(timestamp + 1, ""),
+                              [](const pair<int, string>& lhs,
+                                 const pair<int, string>& rhs) {
+                                  return lhs.first < rhs.first;
+                              });
+        return it != lookup_[key].cbegin() ? prev(it)->second : "";
+    }
+    
+private:
+    unordered_map<string, vector<pair<int, string>>> lookup_;
+};
+
+/**
+ * Your TimeMap object will be instantiated and called as such:
+ * TimeMap* obj = new TimeMap();
+ * obj->set(key,value,timestamp);
+ * string param_2 = obj->get(key,timestamp);
+ */
+