LINE Coding Interview Questions
25 LINE coding interview problems with full optimal solutions — 12 easy, 10 medium, 3 hard. Every problem ships with multiple approaches (brute-force first, then the optimal), complexity tables for each, company-specific tips on what an LINE interviewer values, and a FAQ section.
Showing 10 problems of 25
- #13mediumfoundational
13. LRU Cache
Design a least-recently-used cache with O(1) get and put — LINE uses this to gauge how cleanly you wire a hash map to a doubly linked list, the exact shape behind their chat-message read-state cache.
- #14mediumfoundational
14. Number of Islands
Count the number of distinct islands in a 2D grid of land and water — LINE uses this to gauge whether you reach for clean DFS/BFS flood-fill before more exotic structures.
- #15mediumfoundational
15. Kth Largest Element in an Array
Return the k-th largest element in an unsorted array — LINE uses this to see whether you reach for a min-heap of size k, the same shape as picking the top-k most-active chat rooms.
- #16mediumfoundational
16. Product of Array Except Self
For each index, return the product of every other element without using division — LINE uses this to test prefix/suffix-pass thinking, the same backbone of their read-receipt aggregation.
- #17mediumfoundational
17. Coin Change
Find the fewest coins that make up an amount — LINE uses this to test DP intuition before they push you into LINE Pay reconciliation problems.
- #18mediumfoundational
18. Top K Frequent Elements
Return the k most frequent elements from an array — LINE uses this to gauge whether you reach for bucket sort by frequency, the same shape behind top-k sticker ranking.
- #19mediumfoundational
19. Find All Anagrams in a String
Return all start indices of substrings in s that are anagrams of p — LINE uses this to verify your sliding-window character-count instincts before chat-search problems.
- #20mediumfoundational
20. Subarray Sum Equals K
Count contiguous subarrays whose sum equals k — LINE uses this to test prefix-sum + hash-map reflexes, the engine behind their transaction-rollup audit jobs.
- #21mediumfoundational
21. Daily Temperatures
For each day, find how many days until a warmer temperature — LINE uses this to gauge whether you reach for a monotonic stack, the same primitive behind their next-read-receipt scan.
- #22mediumfoundational
22. Design Underground System
Design a system that records check-ins and check-outs and reports average travel time between stations — LINE uses this to test event-pairing and rolling-average design, the same shape as their delivery-receipt latency tracker.