Time Based Key-Value Store

Author: anantkaushik

981-time-based-key-value-store.py

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+"""
+Problem Link: https://leetcode.com/problems/time-based-key-value-store/
+
+Create a timebased key-value store class TimeMap, that supports two operations.
+1. set(string key, string value, int timestamp)
+Stores the key and value, along with the given timestamp.
+2. get(string key, int timestamp)
+
+Returns a value such that set(key, value, timestamp_prev) was called previously, 
+with timestamp_prev <= timestamp.
+If there are multiple such values, it returns the one with the largest timestamp_prev.
+If there are no values, it returns the empty string ("").
+ 
+Example 1:
+
+Input: inputs = ["TimeMap","set","get","get","set","get","get"], 
+inputs = [[],["foo","bar",1],["foo",1],["foo",3],["foo","bar2",4],["foo",4],["foo",5]]
+Output: [null,null,"bar","bar",null,"bar2","bar2"]
+
+Explanation:   
+TimeMap kv;   
+kv.set("foo", "bar", 1); // store the key "foo" and value "bar" along with timestamp = 1   
+kv.get("foo", 1);  // output "bar"   
+kv.get("foo", 3); // output "bar" since there is no value corresponding to foo at timestamp 3 
+                  // and timestamp 2, then the only value is at timestamp 1 ie "bar"   
+kv.set("foo", "bar2", 4);   
+kv.get("foo", 4); // output "bar2"   
+kv.get("foo", 5); //output "bar2"   
+
+Example 2:
+Input: inputs = ["TimeMap","set","set","get","get","get","get","get"], 
+inputs = [[],["love","high",10],["love","low",20],["love",5],["love",10],
+         ["love",15],["love",20],["love",25]]
+Output: [null,null,null,"","high","high","low","low"]
+ 
+Note:
+All key/value strings are lowercase.
+All key/value strings have length in the range [1, 100]
+The timestamps for all TimeMap.set operations are strictly increasing.
+1 <= timestamp <= 10^7
+TimeMap.set and TimeMap.get functions will be called a total of 120000 times (combined) per test case.
+"""
+# Time Complexity: set -> O(1), get -> O(logn)
+# Space Complexity: O(n)
+import collections
+class TimeMap:
+
+    def __init__(self):
+        """
+        Initialize your data structure here.
+        """
+        self.map = collections.defaultdict(list)
+        
+
+    def set(self, key: str, value: str, timestamp: int) -> None:
+        self.map[key].append((timestamp, value))
+
+    def get(self, key: str, timestamp: int) -> str:
+        keyValues = self.map.get(key)
+        if not keyValues:
+          return ""
+        index = self.binarySearch(keyValues, timestamp)
+        print(index)
+        return keyValues[index][1] if keyValues[index][0] <= timestamp else ""
+        
+    def binarySearch(self, keyValues, timestamp):
+      start, end = 0, len(keyValues) - 1
+      while start < end:
+        mid = start+(end-start+1)//2
+        if keyValues[mid][0] > timestamp:
+          end = mid - 1
+        else:
+          start = mid
+      return end
+
+
+# Your TimeMap object will be instantiated and called as such:
+# obj = TimeMap()
+# obj.set(key,value,timestamp)
+# param_2 = obj.get(key,timestamp)