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

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

Implement Plus One | Coinbase Interview Question

Implement Plus One

Last updated: Apr 2, 2026

Quick Overview

This question evaluates proficiency in array manipulation, elementary arithmetic operations such as carry propagation, and careful handling of edge cases while meeting time and space complexity constraints.

Coinbase

Mar 17, 2026, 12:00 AM

Data Scientist

Onsite

Coding & Algorithms

Given an integer represented as an array of digits digits, where the most significant digit comes first, return the array representing the integer plus one.

Assume:

digits contains only values from 0 to 9
the integer has no leading zeros unless it is exactly zero

Examples:

[1, 2, 3] -> [1, 2, 4]
[4, 3, 2, 1] -> [4, 3, 2, 2]
[9, 9, 9] -> [1, 0, 0, 0]

Implement the solution in Python. Aim for O(n) time and O(1) extra space apart from the returned array.

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