Python Key-Value Program

MediumPython

Problem

Beyondsoft configuration rollout tooling records key-value updates over time. Given the update history and a set of query timestamps, return the complete configuration snapshot visible at each query time.

An update is represented as [timestamp, key, value]. Timestamps are integers and are not necessarily provided in sorted order. If value is null, the key is deleted. Every update with timestamp <= query_timestamp must be applied before producing that query's snapshot. Query results must remain in the same order as the input queries.

Formal Specification

Implement reconstruct_snapshots(operations, queries).

operations is a list of lists, where each item contains an integer timestamp, a string key, and either a string value or null.
queries is a list of integer timestamps.
Return a list of dictionaries. The item at index i contains the key-value state at queries[i].
The returned snapshots must be independent dictionaries, so later updates must not change earlier results.

Constraints

0 <= len(operations), len(queries) <= 10^5
0 <= timestamp <= 10^9
1 <= len(key) <= 50
Values are strings of length at most 100, or null
Keys and timestamps may repeat

Function Signature

def reconstruct_snapshots(operations, queries):

Formal Specification

Implement reconstruct_snapshots(operations, queries).

operations is a list of lists, where each item contains an integer timestamp, a string key, and either a string value or null.
queries is a list of integer timestamps.
Return a list of dictionaries. The item at index i contains the key-value state at queries[i].
The returned snapshots must be independent dictionaries, so later updates must not change earlier results.