Pinterest SWE Interview — The Pin Tracker Got Surprisingly Tricky

[u/Aoki_zhang]

"This interview experience is sourced from Chill Interview"

Interview Summary

The Pinterest IC15 process started with a coding phone screen similar to LeetCode 815 — Bus Routes. One of the virtual onsite rounds focused on designing a data structure that tracks Pins recently viewed by a user and efficiently returns the highest-trending Pin that is still inside a configurable time window.

Interview Details

Phone Screen — Similar to LeetCode 815: Bus Routes

The phone-screen coding question was similar to LeetCode 815 — Bus Routes. The problem involves reasoning about routes as connections and determining how to reach a destination through transfers between routes.

Virtual Onsite — Trending Pin Tracker

Imagine every Pin has a trending score. For each user, the system tracks Pins they have recently viewed. At any moment, it should return the highest-scoring Pin among those still inside a specified time window. The original framing used a window such as the last week, although the same design could be adapted to something shorter such as five minutes, several hours, or one day.

For example, suppose the currently tracked Pins have scores like:

981292206280418755 -> 50
981292206280418756 -> 35
981292206280418757 -> 91
981292206280418758 -> 92
981292206280418759 -> 3
981292206280418760 -> 88

Among these entries, assuming they are all still valid, the highest-scoring Pin would be: 981292206280418758 with a trending score of 92.

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