Solve set equality and ad log top‑K

Q: Solve set equality and ad log top‑K

This multi-part question evaluates set and multiset operations, frequency counting, top-K computation over time windows, sliding-window and streaming data structures, and character-multiset matching for string construction within the coding & algorithms domain.

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Question

Problem Set (Coding)

1) Check whether two sets are equal

You are given two integer arrays A and B that represent sets, except they may contain duplicates and are not sorted.

Return true if they represent the same mathematical set (same unique elements), otherwise return false.

Example

A = [1,2,2,3] , B = [3,1,2] → true
A = [1,2] , B = [1,2,4] → false

Constraints

0 <= len(A), len(B) <= 2e5
Values fit in 32-bit signed integer.

2) Top-K ads from impression logs + sliding window ingestion

You are given an impression log as a list of events:

events[i] = (timestamp_ms, ad_id)
events is sorted by timestamp_ms ascending.

Part 1 (batch): Given events, a window size W_ms, and an end time T_end, return the top K ad IDs by number of impressions whose timestamps fall in [T_end - W_ms, T_end].

Break ties by smaller ad_id (or specify a deterministic rule).

Part 2 (streaming): Implement a data structure with two operations:

ingestImpression(timestamp_ms, ad_id)
getTopK(T_end, W_ms, K)

such that it efficiently supports a sliding window query over recent impressions.

Assume ingestImpression timestamps are non-decreasing.

3) Can a target string be formed from a source string?

Given two strings source and target, determine if you can form target using characters from source.

Each character in source can be used at most once .
Return true if possible, else false .