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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: Mar 29, 2026

Quick Overview

This question evaluates array manipulation and numeric carry propagation skills, along with the ability to reason about time and space complexity when performing arithmetic on digit lists.

Coinbase

Feb 13, 2026, 12:00 AM

Data Scientist

Onsite

Coding & Algorithms

23 solved

Given a non-empty array of digits representing a non-negative integer, where the most significant digit comes first and each element is in [0, 9], add one to the integer and return the resulting array of digits.

You may not convert the entire array directly into a built-in big integer.

Examples:

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

Discuss the time and space complexity of your approach.

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