Instacart Coding Interview Questions
28 Instacart coding interview problems with full optimal solutions — 16 easy, 10 medium, 2 hard. Every problem ships with multiple approaches (brute-force first, then the optimal), complexity tables for each, company-specific tips on what an Instacart interviewer values, and a FAQ section.
Showing 28 problems of 28
- #17mediumfoundational
17. Number of Islands
Count connected land regions in a 2D grid — Instacart interviewers use this to test whether you can model a store's floor-map zones and traverse them efficiently for pick-path planning.
- #18mediumfoundational
18. Meeting Rooms II
Find the minimum number of rooms required to schedule overlapping meetings — Instacart mirrors this directly onto delivery-window scheduling where overlapping shopper slots compete for the same fulfillment capacity.
- #19mediumfoundational
19. Top K Frequent Elements
Return the k most frequently occurring integers — Instacart uses frequency ranking everywhere from surfacing top-ordered items to ranking stores by pickup volume in real-time catalog queries.
- #20mediumfoundational
20. Word Break
Determine if a string can be segmented using a dictionary — Instacart applies this DP pattern when parsing user-typed grocery queries that contain concatenated product tokens against the catalog word list.
- #21mediumfoundational
21. Network Delay Time
Find the time for a signal to reach all nodes in a weighted graph — Instacart uses this exact shortest-path pattern to estimate worst-case delivery propagation across its fulfillment network.
- #22mediumfoundational
22. Insert Interval
Insert a new interval into a sorted, non-overlapping list and merge as needed — Instacart uses this when a new delivery window is injected into an existing shopper schedule without disturbing confirmed slots.
- #23mediumfoundational
23. Coin Change
Find the minimum number of coins that sum to an amount — Instacart draws on this classic DP pattern when computing the fewest batch trips a shopper should make to cover a list of item weights optimally.
- #24hardfoundational
24. Find Median from Data Stream
Maintain a running median as numbers stream in — Instacart applies this pattern to real-time delivery-time tracking where the median ETA must update on every new completed order without a full re-sort.
- #25mediumfoundational
25. LRU Cache
Design a cache that evicts the least recently used item when full — Instacart caches store inventory snapshots in memory for sub-millisecond catalog reads; LRU eviction keeps the hottest stores resident.
- #26mediumfoundational
26. Course Schedule
Detect whether a set of prerequisite dependencies contains a cycle — Instacart uses topological-sort cycle detection when validating that recipe ingredient substitution chains don't loop back on themselves.
- #27mediumfoundational
27. K Closest Points to Origin
Find the k nearest pickup points to a warehouse — Instacart's last-mile team uses this to assign the closest available shoppers to a new order when multiple drivers are in range.
- #28hardfoundational
28. Minimum Window Substring
Find the shortest substring containing all required characters — Instacart uses the sliding-window pattern when scanning product descriptions for a mandatory set of nutritional keywords in the shortest possible text span.
- #1easyfoundational
1. Two Sum
Find two array indices whose values sum to a target — the warmup Instacart uses to gauge baseline hash-map fluency before pricing or inventory matching follow-ups.
- #2easyfoundational
2. Valid Parentheses
Validate that brackets close in the correct order — Instacart uses this as a stack-discipline check before more involved order-state validation problems.
- #3easyfoundational
3. Merge Two Sorted Lists
Merge two sorted linked lists into one — Instacart maps this onto merging two ETA-sorted delivery queues into a single shopper feed.
- #4easyfoundational
4. Remove Duplicates from Sorted Array
Compact a sorted array in place so each value appears once — Instacart frames this as dedupping a sorted SKU scan from a shopper's bag.
- #5easyfoundational
5. Remove Element
Remove all occurrences of a value in place — Instacart uses this to test in-place array discipline before harder shopper inventory pruning problems.
- #6easyfoundational
6. Search Insert Position
Binary search for insertion point in a sorted array — Instacart uses this to gauge binary-search fluency before pricing-tier lookups.
- #7easyfoundational
7. Plus One
Increment a number represented as an array of digits — Instacart uses it as a carry-propagation warmup before inventory-counter bumps.
- #8easyfoundational
8. Merge Sorted Array
Merge two sorted arrays in place — Instacart frames this as merging a primary shopper bag with overflow items from a backup bag.
- #9easyfoundational
9. Binary Tree Inorder Traversal
In-order traverse a binary tree — Instacart uses this to confirm tree fluency before category-hierarchy walking problems.
- #10easyfoundational
10. Same Tree
Decide if two binary trees are structurally identical — Instacart probes recursion fluency before comparing inventory snapshots across stores.
- #11easyfoundational
11. Symmetric Tree
Check if a binary tree is a mirror of itself — Instacart picks this as a recursion-pairing warmup ahead of layout-symmetry problems.
- #12easyfoundational
12. Maximum Depth of Binary Tree
Compute the max depth of a binary tree — Instacart uses this to gate basic recursion against later store-hierarchy depth questions.
- #13easyfoundational
13. Balanced Binary Tree
Check if a binary tree is height-balanced — Instacart screens recursion-with-bailout fluency before harder routing-tree balance checks.
- #14easyfoundational
14. Minimum Depth of Binary Tree
Find the minimum depth (shortest root-to-leaf path) — Instacart uses BFS preference here to test whether you understand early termination.
- #15easyfoundational
15. Pascal's Triangle
Generate the first N rows of Pascal's triangle — Instacart uses this for array-iteration warmups before promo-tier breakdown problems.
- #16easyfoundational
16. Best Time to Buy and Sell Stock
Compute the max profit from one buy and one sell — Instacart uses this single-pass min-tracking warmup before pricing-window questions.