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 16 problems of 28
- #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.