LeetCode in Kotlin

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.

Solution

import java.util.TreeMap

class TimeMap {
    private val map = hashMapOf<String, TreeMap<Int, String>>()

    fun set(key: String, value: String, timestamp: Int) {
        map.getOrPut(key, ::TreeMap)[timestamp] = value
    }

    fun get(key: String, timestamp: Int): String {
        return map[key]?.floorEntry(timestamp)?.value ?: ""
    }
}

/*
 * Your TimeMap object will be instantiated and called as such:
 * var obj = TimeMap()
 * obj.set(key,value,timestamp)
 * var param_2 = obj.get(key,timestamp)
 */

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