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This is a easy difficulty Coding & Algorithms question, commonly asked during Technical Screen rounds at Roblox.

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This question is commonly asked for Machine Learning Engineer candidates at Roblox during technical interviews.

Find the Most Frequent Log Call | Roblox Coding Question

Find the Most Frequent Log Call

Company: Roblox

Role: Machine Learning Engineer

Category: Coding & Algorithms

Difficulty: easy

Interview Round: Technical Screen

You are given a sequence of application log entries. Each entry contains the name of a function or API call made by the system. Write a function that returns the call that appears most frequently in the logs, along with its frequency. Example: - Input: ["login", "search", "login", "checkout", "search", "login"] - Output: ("login", 3) Follow-up discussion can include how to handle ties, how to return the top-k most frequent calls, and how to process logs in a streaming or large-scale setting.

Quick Answer: This question evaluates a candidate's ability to perform frequency analysis on sequences, demonstrating competency with data structures for counting occurrences and with algorithmic time and space complexity considerations.

You are given a sequence of application log entries as a list of strings, where each entry is the name of a function or API call made by the system. Return the call that appears most frequently in the logs, along with its frequency, as a pair `(call, frequency)`. If multiple calls are tied for the highest frequency, return the one that first appears earliest in the log sequence. If the log is empty, return `("", 0)`. Example: - Input: ["login", "search", "login", "checkout", "search", "login"] - Output: ("login", 3) Follow-up directions you could discuss in an interview: how to handle ties, how to return the top-k most frequent calls, and how to process logs in a streaming or large-scale (multi-machine) setting.

Constraints

0 <= len(logs) <= 10^6
Each log entry is a non-empty string of an API/function call name.
Ties are broken by earliest first appearance in the log sequence.
Return ("", 0) for an empty log.

Examples

Input: (["login", "search", "login", "checkout", "search", "login"],)

Expected Output: ("login", 3)

Explanation: "login" appears 3 times, more than "search" (2) and "checkout" (1).

Input: (["a", "b", "a", "b"],)

Expected Output: ("a", 2)

Explanation: "a" and "b" both appear twice; "a" appears first, so it wins the tie.

Input: (["solo"],)

Expected Output: ("solo", 1)

Explanation: A single entry is trivially the most frequent.

Input: ([],)

Expected Output: ("", 0)

Explanation: Empty log returns the sentinel ("", 0).

Input: (["x", "y", "z"],)

Expected Output: ("x", 1)

Explanation: All unique with frequency 1; the earliest-appearing "x" wins the tie.

Input: (["api", "api", "api", "api"],)

Expected Output: ("api", 4)

Explanation: A single repeated call accumulates the full count.

Hints

Use a hash map to count occurrences of each call in a single pass.
Track each call's first-appearance index so you can break frequency ties deterministically.
For the top-k follow-up, a heap of size k or bucket sort by frequency avoids fully sorting all distinct calls; for streaming/large-scale, think Count-Min Sketch or a map-reduce word-count.

Quick Overview

This question evaluates a candidate's ability to perform frequency analysis on sequences, demonstrating competency with data structures for counting occurrences and with algorithmic time and space complexity considerations.