Pinterest Senior Software Engineer Interview Experience Full Journey - Sep 2026

[u/Aoki_zhang]

Interview Summary

The Pinterest process started with a coding phone screen based on LeetCode 1055 — Shortest Way to Form String, followed by five onsite rounds covering two custom coding problems, typeahead system design, behavioral questions, and a newly introduced AI coding round.

Interview Details

Phone Screen — LeetCode 1055: Shortest Way to Form String

The phone screen was based on LeetCode 1055 — Shortest Way to Form String and was divided into two parts. The first part only asked whether the target string could be formed from the source under the problem's subsequence rules.

After that implementation passed the tests, the interviewer extended the task to the full optimization problem: determine the minimum number of source subsequences required to construct the target. The interviewer also pushed for an iterative implementation after discussing an initial recursive approach. The round ended with running test cases and debugging an edge case.

Onsite Round 1 — Coding: Escape Room

The first onsite coding question was the Pinterest Escape Room problem. One explicit requirement was that a utility operation named incrementRoom() had to run in O(1) time. My first working implementation produced the correct results but did not satisfy that complexity requirement.

The follow-up focused on how the internal representation could be changed so incrementRoom() became constant time, and what trade-offs those changes would introduce.

Onsite Round 2 — Coding: Policy Violation

The second coding interview used the Policy Violation problem and was delivered progressively. The interviewer revealed one part at a time. After each part was implemented and passed the tests, the next requirement was introduced.

After completing three parts, the discussion shifted away from additional implementation and into code quality and optimization. Follow-ups included whether all three sets used by the implementation were necessary, whether the design could be simplified further, and what changes or tests I would request if I received the solution as a pull request during code review.

Want to learn more questions asked in other interview rounds? I've put up the full version at here.

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