g0901_1000.s0981_time_based_key_value_store

Class TimeMap

java.lang.Object

g0901_1000.s0981_time_based_key_value_store.TimeMap

public class TimeMap
extends Object

981 - Time Based Key-Value Store.

Medium

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”]

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" 

Constraints:

• 1 <= key.length, value.length <= 100
• key and value consist of lowercase English letters and digits.
• 1 <= timestamp <= 107
• All the timestamps timestamp of set are strictly increasing.
• At most 2 * 105 calls will be made to set and get.

Constructor Summary

Constructors

Constructor and Description
TimeMap()

Method Summary

Modifier and Type	Method and Description
String	get(String key, int timestamp)
void	set(String key, String value, int timestamp)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

TimeMap

public TimeMap()

Method Detail

set

public void set(String key,
                String value,
                int timestamp)

get

public String get(String key,
                  int timestamp)