## Problem You have a single-threaded CPU running `n` functions (0-indexed). You are given a log of start and end events. Compute the exclusive execution time of each function (time spent in that function, not counting nested calls). Log format: `"function_id:start|end:timestamp"` ```python def exclusive_time(n: int, logs: list[str]) -> list[int]: """Return list of length n with exclusive time for each function.""" pass ``` ``` Input: n = 2 logs = ["0:start:0","1:start:2","1:end:5","0:end:6"] Output: [3, 4] # Function 0: runs [0,1] and [6,6] -> 2+1=3 # Function 1: runs [2,5] -> 4 Input: n = 1 logs = ["0:start:0","0:start:2","0:end:5","0:end:6"] Output: [7] ``` ## Follow-ups 1. How does a stack naturally model the nesting of function calls here? 2. What edge cases arise with recursive functions (same function ID appears on the stack multiple times)? 3. If timestamps were floating-point, how would you adjust the interval arithmetic? 4. Extend to multi-threaded execution: each function has a thread ID — what changes?

InterviewDB Experience · USA

Function Time: Compute Exclusive Execution Time of Each Process

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Problem You have a single-threaded CPU running n functions (0-indexed). You are given a log of start and end events. Compute the exclusive execution time of each function (time spent in that function, not counting nested calls). Log format: "function_id:start|end:timestamp" Follow-ups How does a stack naturally model the nesting of function calls here? What edge cases arise with recursive functions (same function ID appears on the stack multiple times)? If timestamps were floating-point, how wou…

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About This Question

This is a candidate experience report from a decagon interview during the phone round.

It covers the following topics: Recursion, Coding, Phone, Stack .

Topics

Recursion Coding Phone Stack

About Decagon Interview Reports

This question was reported by a candidate who interviewed at Decagon. LeakCode aggregates interview reports from 10+ sources, including 1Point3Acres, Glassdoor, LeetCode Discuss, Blind, Reddit, Indeed, and Nowcoder. Each report is translated where necessary, deduplicated against existing entries, and tagged by company, role, round type, and reporting date.

Use this question as one calibration data point, not a memorization target. Companies typically rotate their question pools every 2-4 months; the exact wording of a 2024 question may differ from what you encounter today. The underlying pattern, difficulty level, and follow-up depth at Decagon are the higher-signal extractions to take from this report.

For broader preparation context, the Decagon interview process typically includes a recruiter screen, one or two technical phone screens, and a 4-5 round on-site loop covering coding, system design (at L4+ levels), and behavioral. Reports tagged on LeakCode show the round-by-round distribution and typical difficulty calibration. To browse questions filtered by round type and seniority, use the company hub linked above.

How To Practice This Type of Question

Solve similar problems on LeetCode under timed conditions (25-35 minutes per medium difficulty). The goal is pattern recognition: recognize the underlying technique (sliding window, two-pointer, BFS, memoized recursion, etc.) within 60-90 seconds of reading. Strong candidates verbalize their hypothesis out loud before coding, then iterate based on feedback. Weak candidates dive into implementation immediately, lose time on the wrong approach, and run out of time for follow-ups.

Companies update their question pools every 2-4 months. The exact wording of any given question may have been retired by the time you interview. Focus your prep on the pattern, not the specific problem. The patterns that appear in Decagon reports consistently are the ones worth investing in; one-off niche problems are not.

During Your Decagon Round

Apply the standard interview round template: clarify requirements (2-3 minutes), state your approach out loud and confirm direction with the interviewer (3-5 minutes), code with narration (15-25 minutes), test with concrete examples including edge cases (5 minutes), discuss optimization or trade-offs if time permits (5 minutes). This template is universally accepted across FAANG and adjacent companies; deviating from it produces weaker interviewer feedback signal.

The single most predictive failure mode in Decagon reports tagged "no hire": not asking clarifying questions. Interviewers are explicitly trained to weight this. Strong candidates ask 3-5 clarifying questions even on problems that look obvious; weak candidates dive into code immediately. The clarifying-question check is often the first signal recorded in the interviewer's written notes.