Bloomberg Coding Interview Questions
32 Bloomberg coding interview problems with full optimal solutions — 16 easy, 13 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 Bloomberg interviewer values, and a FAQ section.
Showing 32 problems of 32
- #23hardfoundational
23. Merge K Sorted Lists
Bloomberg's order-book engine merges price-sorted queues from dozens of exchanges every microsecond — this problem tests whether you can do the same efficiently using a min-heap instead of naive repeated merging.
- #42hardfoundational
42. Trapping Rain Water
Calculating trapped water between histogram bars maps directly onto Bloomberg's time-series gap analysis — measuring how much volume pools between market microstructure events — and rewards the two-pointer insight that eliminates extra passes.
- #146mediumfoundational
146. LRU Cache
Bloomberg Terminal caches thousands of live ticker snapshots in memory — this problem tests whether you can build the eviction policy that keeps the most-recently-accessed instruments hot while dropping stale ones in O(1) per operation.
- #153mediumfoundational
153. Find Minimum in Rotated Sorted Array
Bloomberg's market-data systems store price histories as circular buffers that reset at midnight — finding the rotation pivot is the same binary search insight Bloomberg engineers apply when locating the session-open price in a ring buffer.
- #217easyfoundational
217. Contains Duplicate
Bloomberg's data-ingestion pipelines must flag duplicate trade confirmations before they corrupt position ledgers — this warmup problem tests whether you instinctively reach for a hash set instead of nested loops when deduplication speed matters.
- #239mediumfoundational
239. Sliding Window Maximum
Bloomberg's risk engine computes rolling maximum drawdown across a moving time window on live price feeds — this problem tests whether you can deliver those rolling stats in O(n) with a monotonic deque instead of rescanning the window each tick.
- #295hardfoundational
295. Find Median from Data Stream
Bloomberg's real-time analytics dashboard streams millions of trade prices per day and must serve a live median price metric at sub-millisecond latency — this problem tests the two-heap trick that keeps median retrieval O(1) even as data flows in.
- #347mediumfoundational
347. Top K Frequent Elements
Bloomberg's market-intelligence dashboards surface the top-K most actively traded tickers across millions of events per session — this problem tests whether you can identify those leaders in O(n log k) using a min-heap rather than sorting the full frequency table.
- #412easyfoundational
412. Fizz Buzz
Bloomberg uses Fizz Buzz as a pure communication test — they want to hear you enumerate edge cases aloud (divisible by both 3 and 5 first), mirroring how Bloomberg engineers articulate business-rule precedence before touching a trading system's branching logic.
- #560mediumfoundational
560. Subarray Sum Equals K
Bloomberg's compliance team counts how many consecutive trading windows sum to a target P&L threshold — this is exactly the subarray-sum problem, and the prefix-sum hash-map trick cuts the search from O(n^2) to a single pass every real-time analyst depends on.
- #621mediumfoundational
621. Task Scheduler
Bloomberg's batch-job infrastructure schedules thousands of daily data-refresh tasks under cooldown constraints between repeated runs — this problem captures that scheduling logic and tests whether you can compute minimum total time using a greedy frequency analysis instead of simulation.
- #973mediumfoundational
973. K Closest Points to Origin
Bloomberg's geo-analytics tools identify the K nearest branch offices or client locations to a reference point — this problem tests whether you apply a max-heap of size K for a clean O(n log K) solution instead of sorting the entire dataset when K is small.
- #1easyfoundational
1. Two Sum
Two Sum is the canonical Bloomberg warm-up: return the indices of two numbers in an array that add to a given target. Bloomberg uses it on phone screens to gauge whether you can narrate the space-for-time tradeoff before reaching for the optimal one-pass hash map.
3 free resourcesSolve → - #3mediumcompany favorite
3. Longest Substring Without Repeating Characters
Given a string, find the length of the longest substring without repeating characters. Bloomberg uses this as their canonical sliding-window question — they want a clean O(n) two-pointer with a hash map storing last-seen indices.
3 free resourcesSolve → - #7mediumfrequently asked
7. Reverse Integer
Reverse the digits of a 32-bit signed integer, returning 0 on overflow. Bloomberg uses this specifically to test whether you handle the 32-bit integer overflow check correctly — finance code at Bloomberg routinely cares about numeric boundaries.
3 free resourcesSolve → - #9easyfrequently asked
9. Palindrome Number
Given an integer x, return true if x is palindrome. Bloomberg uses this as a follow-up to Reverse Integer — they want to see the without-converting-to-string optimization to test whether you can think about numeric problems numerically.
3 free resourcesSolve → - #13easyfoundational
13. Roman to Integer
Convert a Roman-numeral string to an integer. Bloomberg uses this to test whether you can handle the subtractive notation (IV, IX, XL, XC, CD, CM) elegantly — the obvious solution has six special cases, the elegant one has none.
3 free resourcesSolve → - #14easyfrequently asked
14. Longest Common Prefix
Find the longest common prefix shared by an array of strings. Bloomberg uses this as a string-iteration test — they want clean code that handles the empty-input edge and discusses vertical vs horizontal scan tradeoffs.
3 free resourcesSolve → - #20easyfoundational
20. Valid Parentheses
Given a string containing only the characters '(', ')', '{', '}', '[' and ']', determine if it is balanced. Bloomberg asks this as a stack-fluency check: can you spot the data structure without prompting and implement it correctly on the first try.
3 free resourcesSolve → - #21easyfoundational
21. Merge Two Sorted Lists
Splice two ascending linked lists into one sorted list. Bloomberg uses this to test pointer hygiene and the dummy-head trick — they want clean code with no special-case branching for the empty-list edge.
3 free resourcesSolve → - #28easyfrequently asked
28. Find the Index of the First Occurrence in a String
Implement strStr() — return the index of the first occurrence of needle in haystack, or -1. Bloomberg uses this as the gateway to substring algorithms: brute force is fine for warm-up, but they always probe for KMP if the conversation goes deeper.
3 free resourcesSolve → - #53mediumcompany favorite
53. Maximum Subarray
Find the contiguous subarray with the largest sum. Bloomberg uses Kadane's algorithm as the gateway to dynamic-programming questions — they want to see you derive the recurrence (current_max = max(num, current_max + num)) on the board.
3 free resourcesSolve → - #56mediumcompany favorite
56. Merge Intervals
Given an array of intervals, merge all overlapping intervals. Bloomberg uses this to test the sort-then-sweep pattern that shows up in calendar, market-hours, and time-window problems across their data-infrastructure teams.
3 free resourcesSolve → - #57mediumfrequently asked
57. Insert Interval
Insert a new interval into a sorted list of non-overlapping intervals, merging as needed. Bloomberg uses this as the Merge Intervals follow-up — same shape but O(n) instead of O(n log n) because the input is pre-sorted.
3 free resourcesSolve → - #121easycompany favorite
121. Best Time to Buy and Sell Stock
Given a daily price series, return the maximum profit from one buy + one sell. Bloomberg leans on this for finance-engineering candidates — it's a single-pass greedy that mirrors the real-world 'running max profit' calculation traders care about.
3 free resourcesSolve → - #125easyfrequently asked
125. Valid Palindrome
Given a string, determine if it's a palindrome after removing non-alphanumeric characters and ignoring case. Bloomberg uses this to test two-pointer fluency plus a careful handling of mixed-content strings.
3 free resourcesSolve → - #136easyfrequently asked
136. Single Number
Every element appears twice except one. Find the one. Bloomberg uses this to test the XOR trick — they want the linear-time, constant-space solution, not the hash-set fallback.
3 free resourcesSolve → - #168easyfrequently asked
168. Excel Sheet Column Title
Convert a positive integer to its Excel-style column title (A, B, ..., Z, AA, AB, ...). Bloomberg uses this to test whether you can handle a base-26 conversion with the 1-indexed twist that breaks standard base-conversion code.
3 free resourcesSolve → - #206easyfoundational
206. Reverse Linked List
Reverse a singly linked list. Bloomberg uses this as a linked-list fluency check — they want to see both the iterative pointer-rewire and the recursive version, plus an articulate reason for picking one over the other.
3 free resourcesSolve → - #268easyfrequently asked
268. Missing Number
An array of n distinct numbers in [0, n] is missing one. Find it. Bloomberg uses this to test whether you know multiple O(n)/O(1) tricks — sum formula AND XOR fold — and can pick between them based on the input constraints.
3 free resourcesSolve → - #287mediumfrequently asked
287. Find the Duplicate Number
An array of n+1 integers in [1, n] contains exactly one duplicate. Find it without modifying the array and in O(1) extra space. Bloomberg uses this as a classic 'two constraints, no obvious trick' problem to see if you reach for Floyd's cycle detection.
3 free resourcesSolve → - #387easyfrequently asked
387. First Unique Character in a String
Given a string, find the index of the first non-repeating character, or -1 if all repeat. Bloomberg uses this as a hash-map fluency warm-up — they want a two-pass O(n) with a discussion of LinkedHashMap (or ordered Map) as an alternative.
3 free resourcesSolve →
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