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Compute unique duration by merging intervals

Last updated: Mar 29, 2026

Quick Overview

This question evaluates a data engineer's proficiency in temporal data manipulation and interval-set reasoning using SQL and Python, specifically skills in merging overlapping intervals and computing deduplicated cumulative durations.

  • easy
  • Nuro
  • Data Manipulation (SQL/Python)
  • Data Engineer

Compute unique duration by merging intervals

Company: Nuro

Role: Data Engineer

Category: Data Manipulation (SQL/Python)

Difficulty: easy

Interview Round: Technical Screen

## Problem You have an autonomous-driving clip dataset where each row represents a time interval from a driving run. ### Table: `clips` | column | type | description | |---|---|---| | `set_id` | INT | Session/clip set identifier (e.g., 1–6) | | `run_id` | STRING | Driving run identifier, formatted like `YYYYMMDD_HHMMSS` | | `start_time` | INT | Clip start time offset (e.g., seconds) | | `end_time` | INT | Clip end time offset (e.g., seconds) | | `set_number` | INT | Dataset/source identifier | Assume each interval is **half-open**: `[start_time, end_time)` so duration is `end_time - start_time`. Intervals for the same `run_id` may: - overlap (partially or fully), - be duplicated/redundant, - have gaps (non-contiguous). ## Task Compute, for **each `run_id`**, the **cumulative deduplicated time**: the total duration covered by the **union** of all intervals for that `run_id` (i.e., after merging overlaps). ## Example input For run `20250101_122334`: - set 1: `[58, 70)` - set 2: `[57, 69)` - set 3: `[55, 72)` - set 4: `[56, 71)` - set 5: `[80, 100)` For run `20250102_101010`: - set 6: `[43, 62)` ## Expected output Return a result with: - `run_id` - `cumulative_unique_time` (same unit as the time offsets) Using the example above, results would be: - `20250101_122334` → `39` - `20250102_101010` → `19` ## Requirements 1. Write a **SQL** solution to compute `cumulative_unique_time` per `run_id`. 2. Write a **Python** solution to compute the same metric (given a list/dataframe of intervals).

Quick Answer: This question evaluates a data engineer's proficiency in temporal data manipulation and interval-set reasoning using SQL and Python, specifically skills in merging overlapping intervals and computing deduplicated cumulative durations.

Nuro logo
Nuro
Jul 8, 2025, 12:00 AM
Data Engineer
Technical Screen
Data Manipulation (SQL/Python)
4
0

Problem

You have an autonomous-driving clip dataset where each row represents a time interval from a driving run.

Table: clips

columntypedescription
set_idINTSession/clip set identifier (e.g., 1–6)
run_idSTRINGDriving run identifier, formatted like YYYYMMDD_HHMMSS
start_timeINTClip start time offset (e.g., seconds)
end_timeINTClip end time offset (e.g., seconds)
set_numberINTDataset/source identifier

Assume each interval is half-open: [start_time, end_time) so duration is end_time - start_time.

Intervals for the same run_id may:

  • overlap (partially or fully),
  • be duplicated/redundant,
  • have gaps (non-contiguous).

Task

Compute, for each run_id, the cumulative deduplicated time: the total duration covered by the union of all intervals for that run_id (i.e., after merging overlaps).

Example input

For run 20250101_122334:

  • set 1: [58, 70)
  • set 2: [57, 69)
  • set 3: [55, 72)
  • set 4: [56, 71)
  • set 5: [80, 100)

For run 20250102_101010:

  • set 6: [43, 62)

Expected output

Return a result with:

  • run_id
  • cumulative_unique_time (same unit as the time offsets)

Using the example above, results would be:

  • 20250101_122334 → 39
  • 20250102_101010 → 19

Requirements

  1. Write a SQL solution to compute cumulative_unique_time per run_id .
  2. Write a Python solution to compute the same metric (given a list/dataframe of intervals).

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