#981

Time Based Key-Value Store

medium · 49.8% accepted · 5,249 likes · top 37%

hash table · string · binary search · design

Description

Design a time-based key-value data structure that can store multiple values for the same key at different time stamps and retrieve the key's value at a certain timestamp.

Implement the TimeMap class:

- TimeMap() Initializes the object of the data structure.

- void set(String key, String value, int timestamp) Stores the key key with the value value at the given time timestamp.

- String get(String key, int timestamp) Returns a value such that set was called previously, with timestamp_prev <= timestamp. If there are multiple such values, it returns the value associated with the largest timestamp_prev. If there are no values, it returns "".

Example 1:

Input

["TimeMap", "set", "get", "get", "set", "get", "get"]

[[], ["foo", "bar", 1], ["foo", 1], ["foo", 3], ["foo", "bar2", 4], ["foo", 4], ["foo", 5]]

Output

[null, null, "bar", "bar", null, "bar2", "bar2"]

Example 2:

Explanation

TimeMap timeMap = new TimeMap();

timeMap.set("foo", "bar", 1); // store the key "foo" and value "bar" along with timestamp = 1.

timeMap.get("foo", 1); // return "bar"

timeMap.get("foo", 3); // return "bar", since there is no value corresponding to foo at timestamp 3 and timestamp 2, then the only value is at timestamp 1 is "bar".

timeMap.set("foo", "bar2", 4); // store the key "foo" and value "bar2" along with timestamp = 4.

timeMap.get("foo", 4); // return "bar2"

timeMap.get("foo", 5); // return "bar2"

Solution