added time-based key val leetcode problem in cpp

121 Leetcode/time_based_key_val.cpp

@@ -0,0 +1,27 @@
+#include<bits/stdc++.h>
+using namespace std;
+
+class TimeMap {
+public:
+    // initialising data structure as string=> {int,string}
+    unordered_map<string, vector<pair<int, string>>> m;
+    TimeMap() {
+    }
+    void set(string key, string value, int timestamp) {
+        m[key].push_back({timestamp, value});
+    }
+    string get(string key, int timestamp) {
+        if(!m.count(key))
+            return "";
+            // binary search 
+        int start = 0, end = m[key].size();
+        while(start < end) {
+            int mid = start + (end-start)/2;
+            if(m[key][mid].first > timestamp)
+                end = mid;
+            else
+                start = mid + 1;
+        }
+        return start > 0 and start <= m[key].size() ? m[key][start-1].second : "";
+    }
+};