How do I approach Coding & Algorithms interview questions?

Coding & Algorithms questions require understanding of core concepts and practice. PracHub provides solutions with explanations to help you master coding & algorithms interviews.

What difficulty level is this interview question?

This is a Medium difficulty Coding & Algorithms question, commonly asked during Onsite rounds at Apple.

What role is this question designed for?

This question is commonly asked for Data Scientist candidates at Apple during technical interviews.

Find Smallest Missing Positive Integer in O(n) Time

Last updated: Mar 29, 2026

Quick Overview

This question evaluates a candidate's skill in array algorithms and in-place algorithm design, emphasizing understanding of time and space complexity and handling edge cases when identifying the smallest missing positive integer.

Medium
Apple
Coding & Algorithms
Data Scientist

Apple

Aug 4, 2025, 10:55 AM

Data Scientist

Onsite

Coding & Algorithms

Scenario

LeetCode-style algorithm phone interview

Question

Implement a function that returns the smallest missing positive integer in an unsorted integer array in O(n) time and O(

space, then explain the complexity trade-offs.

Hints

Use index placement/cyclic sort to achieve constant extra space.

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