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154 questions. A concrete next step.
104 coding exercises with authored examples and private grading cases, plus 50 system-design scenarios with constraints and failure rounds.
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154 of 154 original questions
Daily signal total
A career dashboard receives n signed activity changes. Return their total without changing their order or values.
Unique practice visitors
Visitor IDs may repeat in the practice log. Count how many distinct integer IDs occurred.
Best practice momentum
Daily momentum can rise or fall. Find the maximum sum of a nonempty contiguous segment of the daily changes.
Pair a mentoring budget
Count index pairs i < j whose activity costs add to the target budget. Equal values at different indexes count separately.
Find the first available slot
Given sorted availability scores, return the zero-based index of the first score at least the target. Return n if none qualifies.
Minimum review capacity
Review n positive workloads in order across at most d days. Each day takes a contiguous group. Find the smallest daily capacity that can complete every workload.
Longest focused practice window
Each activity is labeled by an integer topic ID. Find the longest contiguous window containing at most k distinct topics.
Validate nested actions
Positive IDs open actions; negative IDs close the matching positive ID. Actions must close in reverse opening order. Print 1 if the entire sequence is correctly nested and fully closed, otherwise 0.
Concurrent mentoring rooms
Mentoring sessions use half-open intervals [start, end). Find the minimum number of rooms needed. A room ending at time t can be reused by a session starting at t.
Fewest connection hops
Given an undirected unweighted graph, return the fewest edges from source to target, or -1 if unreachable. Duplicate edges and self-loops are allowed.
Minimum practice tokens
You have unlimited tokens of each given positive value. Return the fewest tokens needed to total exactly the target, or -1 if impossible.
Longest growing milestones
Find the length of the longest strictly increasing subsequence of milestone scores. A subsequence preserves order but may skip entries; equal scores do not extend it.
Rain storage between walls
Walls have unit width and nonnegative integer heights. Return the total water trapped after rain.
Runner-up distinct score
Return the second largest DISTINCT score, or -101 if fewer than two distinct scores exist.
Crossed arrival pairs
Count pairs i < j for which value[i] > value[j]. Equal values do not count.
Majority topic ID
Return the topic ID occurring strictly more than n/2 times, or -101 if no such ID exists.
Missing sequence ID
The n supplied IDs are distinct members of 0..n. Return the one missing ID.
First positive inventory gap
Return the smallest positive integer absent from the supplied values.
Group active flags with swaps
Swap any two positions per move. Find the fewest swaps needed to place all 1 flags in one contiguous group. Return 0 when there are no 1 flags.
One inventory trade gain
Buy once and later sell once, or do nothing. Return the maximum nonnegative gain from the daily prices.
Repeat inventory trade gain
Buy and sell repeatedly but hold at most one unit at a time. No fees or cooldown apply. Return the greatest total gain.
Smallest sorting repair span
Return the length of the smallest contiguous segment whose sorting makes the whole array nondecreasing. Return 0 if already sorted.
Peak product segment
Return the largest product of a nonempty contiguous segment. Zeros and negative values are allowed.
Consecutive topic ID run
Return the length of the longest run of consecutive distinct integer values, regardless of their input order.
Count target-sum segments
Count nonempty contiguous segments whose sum equals the target.
Shortest positive target window
Return the minimum length of a nonempty contiguous segment whose sum is at least target; return 0 if none qualifies.
Product budget windows
Count nonempty contiguous segments whose product is strictly below k.
Exactly k topic windows
Count nonempty contiguous segments containing exactly k distinct values.
Longest balanced flag span
Return the longest contiguous span containing equally many zeros and ones.
Longest streak with flip budget
Flip at most k zero flags into ones. Return the longest achievable contiguous one streak.
Fixed-window peak workload
Return the maximum sum among contiguous windows of exactly k values. Negative sums remain negative.
Rotated ID lookup
A strictly increasing array was cyclically rotated. Return the zero-based target index, or -1 if absent.
Smallest rotated checkpoint
Return the smallest value of a rotated strictly increasing array.
Mountain summit index
Values strictly increase then strictly decrease, with the summit strictly inside the array. Return its zero-based index.
Rank in merged sorted logs
Merge two nondecreasing logs conceptually. Return the k-th smallest value, with k one-based. Duplicates count separately.
Integer square-root floor
Return floor(sqrt(x)) without requiring floating-point root operations.
Minimum batch processing rate
Each hour processes at most rate units from one workload; leftover hourly capacity is not shared. Find the minimum positive integer rate finishing all workloads within h hours.
Twice the merged median
Return TWICE the median of two nondecreasing arrays, so the output remains an integer. For even length add the two central values; for odd length double the central value.
Largest histogram cover
Each bar has width one. Return the largest rectangular area lying completely under consecutive histogram bars.
Total wait for warmer readings
For each reading, wait until the first later STRICTLY larger reading; if none exists, its wait is zero. Return the sum of all index waits.
Visible rooftop pairs
Count pairs i<j that can see each other: every intermediate height must be strictly below min(height[i],height[j]). Adjacent rooftops always qualify.
Sum of all segment minimums
For every nonempty contiguous segment take its minimum. Return the sum of these minimums.
Sum of rolling window peaks
Take the maximum of each length-k contiguous window and return the sum of these maxima.
Evaluate postfix instructions
Evaluate a valid postfix expression. Operands are integers -10..10; tokens 101,102,103 mean addition, subtraction and multiplication. Subtraction uses left operand minus right operand.
Minimum action-bracket insertions
Tokens 1 and -1 mean open and close brackets of one kind. Return the fewest bracket insertions needed to make the entire sequence balanced.
Maximum action nesting depth
Given a valid balanced bracket sequence encoded as 1=open and -1=close, return its maximum nesting depth.
Longest balanced action segment
Return the length of the longest contiguous VALID balanced bracket segment encoded as 1=open and -1=close. Balanced totals alone do not ensure valid prefixes.
Front after queue commands
Each command pair is (1,x) to enqueue x or (2,0) to remove the front if present. Return the final front, or -101 for an empty queue.
Largest shared batch divisor
Return the greatest positive integer dividing every supplied positive batch size.
Coprime partner pairs
Count index pairs i<j whose positive values have greatest common divisor 1.
Prime-numbered tickets
Count prime integers in the inclusive range 0..x.
Trailing factorial zeros
Return the number of trailing decimal zeros in x!, with 0!=1. Do not construct the factorial.
Modular retry multiplier
Return base^exponent modulo modulus. Define exponent zero as yielding 1 before taking the modulus.
Committee selection count
Count unordered ways to choose exactly r different people from n. Return 0 for r>n. People are distinct and order does not matter.
Fewest square-valued tokens
Return the minimum number of positive perfect squares that sum to x. Squares may repeat; x=0 needs zero tokens.
Total binary set-bit marks
Add the number of one bits in the binary representation of every integer from 0 through x, inclusive.
Digit-square convergence
Repeatedly replace a positive integer with the sum of squares of its decimal digits. Print 1 if this reaches 1, otherwise 0 when a cycle repeats.
Longest mirrored glyph span
Return the length of the longest nonempty contiguous palindromic glyph sequence.
Count mirrored glyph spans
Count all nonempty palindromic contiguous glyph sequences. Equal content at different indexes counts separately.
Minimum mirrored partition cuts
Partition the glyph sequence into contiguous palindromes. Return the fewest cuts between parts.
Glyph edit distance
Return the fewest single-glyph insertions, deletions and substitutions converting the first sequence to the second. Every operation costs one.
Shared glyph subsequence length
Return the length of the longest sequence that is a subsequence of both inputs. Subsequence order is preserved but indexes may be skipped.
Shared contiguous glyph block
Return the length of the longest contiguous glyph block occurring in both inputs. Skipping characters is not allowed.
Target glyph subsequence count
Count indexed subsequences of the first input equal to the second input. Return the count modulo 1,000,000,007.
Shortest glyph coverage window
Return the shortest contiguous source window containing every target glyph with at least its target multiplicity. Return 0 if no covering window exists.
Anagram glyph window count
Count contiguous source windows that are permutations of the target glyph sequence, including target multiplicities.
Run-compressed glyph length
Compress each consecutive run as one glyph plus the decimal run count when the run is longer than one. Return the resulting encoded length; the glyph always occupies one symbol.
Longest unrepeated glyph window
Return the length of the longest contiguous glyph sequence with no repeated glyph.
Digit message decoding count
A=1 through Z=26. Count ways to decode the full digit sequence. Zero cannot stand alone; a pair may not begin with zero. Return the count modulo 1,000,000,007.
Routes through a blocked grid
Start at the top-left and move only right or down to the bottom-right. Zero cells are open and one cells blocked. Count routes modulo 1,000,000,007; blocked endpoints yield zero.
Minimum route charge
Move right/down from top-left to bottom-right. Return the minimum total charge including both endpoints.
Island cluster count
One cells are land. Count connected land components using four-side adjacency.
Largest island footprint
Return the cell count of the largest four-side connected land component, or 0 if no land exists.
Total land border length
Return the number of land-cell sides touching water or outside the grid. Multiple islands and enclosed water are allowed.
Shortest blocked-grid exit route
Cells encode 0=open, 1=blocked, 2=start and 3=exit. Return the fewest four-side moves from start to exit, or -1 if unreachable.
Total distance to nearest zero
For each cell measure the fewest four-side moves to any zero cell; one cells are walkable. Return the sum of these distances.
Largest solid square area
Return the area of the largest axis-aligned square containing only one cells, or 0 when no land exists.
Rooted mentoring tree height
Return the maximum number of edges from root 0 to any node. A single-node tree has height 0.
Mentoring tree leaf count
Count nodes with no children in the rooted tree, including the root when it is the only node.
Best root-to-leaf evidence weight
Nodes have signed weights. Return the maximum sum on a ROOT-TO-LEAF path, including endpoints. Do not stop early at an internal node.
Mentoring tree diameter
Return the greatest edge distance between any two nodes of the tree. Direction from parents does not constrain the path.
Fewest reviewers covering tree edges
Select as few tree nodes as possible so every parent-child edge has at least one selected endpoint. Return the minimum selected-node count.
Strict search-tree check
Print 1 if the supplied binary tree satisfies strict BST ordering, otherwise 0. Every value in a left subtree must be smaller and every value in a right subtree larger; duplicates invalidate it.
Disconnected network groups
Count connected components of the undirected graph, including isolated vertices.
Can the network form two teams?
Print 1 if vertices can be colored with two colors so every undirected edge joins different colors; otherwise 0. Self-loops invalidate it.
Undirected loop check
Print 1 if the undirected multigraph contains a cycle, otherwise 0. A self-loop is a cycle; two parallel edges form a cycle.
Directed dependency loop check
Edges are directed. Print 1 if a directed cycle exists, otherwise 0.
Count valid dependency orders
Count vertex permutations in which every directed edge u→v places u before v. Cyclic inputs have zero orders.
Longest ordered dependency chain
Every directed edge points from a smaller vertex ID to a larger one. Return the longest path’s number of edges, allowing any start and end.
Cheapest directed service route
Return the cheapest directed source-to-target route cost, or -1 if unreachable. Source equals target has cost zero.
Minimum network wiring cost
Edges are undirected. Return the cheapest total edge cost connecting all vertices, or -1 if impossible. A one-vertex network costs zero.
Cheapest route with a hop limit
Find the cheapest directed route using AT MOST k edges, not k intermediate stops. Return -1 if none qualifies.
Critical network vertices
Count vertices whose removal, including incident edges, increases the number of connected components of the UNDIRECTED graph. Compare with the original component count.
Critical network edges
Count undirected edges whose individual removal increases the connected-component count. Parallel edges are separate: removing one may leave another route.
Mutual reachability groups
Count strongly connected components of a directed graph. Every pair of vertices within one group can reach each other.
Maximum mentor assignment matching
Assign left-side learners to compatible right-side mentors. Each learner and mentor may appear in at most one assignment. Return the maximum assignment count.
Most non-overlapping sessions
Select as many sessions as possible with no overlap. Sessions are half-open [start,end), so touching endpoints are compatible.
Deadline reward schedule
Each job takes one time slot and earns its nonnegative reward only if completed by its integer deadline. Slots are numbered from one. Return maximum total reward; a job can run at most once.
Minimum log merge cost
Merge any two positive log sizes for cost equal to their sum; the merged log has that size. Repeat until one log remains. Return the minimum total cost.
First feasible refueling start
Each station supplies fuel and has a cost to travel to the next station, with the last wrapping to zero. Start with an empty tank. Return the smallest zero-based start index completing one full loop without a negative tank, or -1.
Cache misses in a request trace
An initially empty cache holds at most capacity keys. Every request makes its key most recently used. A missing key counts as one miss and is inserted, evicting the least recently used key if full. Return the miss count.
Rolling request admission
Process nondecreasing request timestamps. Admit a request only if fewer than limit previously ADMITTED requests lie in (time - window, time]. Rejected requests do not consume capacity. Equal timestamps are distinct requests. Return the admitted count.
Notification cooldown
Deliver the first notification for each user. Deliver another only when at least cooldown time has passed since that user’s last DELIVERED notification. Ignored notifications do not restart cooldown. Return the delivered count.
Peak load after batch updates
Start with n zero-valued slots. Each update adds a nonnegative amount to every slot in the inclusive range [left,right]. Return the largest final slot value.
Reliable practice notifications
Design a service that reminds learners about scheduled practice. Support email and push, local time zones, opt-outs and delivery history.
Searchable work artifact library
Design a community library where learners voluntarily publish code/design artifacts and reviewers leave structured feedback. Private drafts must stay private.
Multi-tenant coding assessment service
Design a code execution service for timed assessments. Keep hidden tests private and isolate arbitrary submissions from application credentials and other tenants.
Fair API rate limits
Limit API usage across free and paid tenants while retaining clear retry behavior.
Revocable short links
Create short public links with expiration, click analytics and abuse controls.
Reliable chat delivery
Support one-to-one chat, offline delivery and per-conversation ordering.
Personalized activity feed
Build a feed of followed creators with private-account permissions and muted topics.
Product catalog search
Search products by text, category and price while preserving stock freshness.
Timed ticket reservations
Sell limited seats with temporary holds, payments and cancellation.
Payment webhook reconciliation
Consume provider payment events and maintain an auditable order payment state.
Multi-service order workflow
Coordinate checkout, inventory, payment and fulfillment across independent services.
Resumable large-file uploads
Upload large work artifacts with interruption recovery, access control and scanning.
Versioned read cache
Cache frequently read profile summaries while supporting owner updates and deletion.
Session revocation service
Manage browser/device sessions, logout-all and account risk actions.
Structured log ingestion
Collect application logs for tenant-scoped debugging and retention.
Metrics and alert delivery
Collect service metrics and notify operators when rules breach thresholds.
Feature flag configuration delivery
Serve flags to clients with staged rollouts and rollback.
Nearby driver dispatch
Match riders with nearby available drivers and confirm one assignment.
Concurrent document editing
Support shared document editing, offline reconnect and version history.
Conflict-aware calendar booking
Book interviewer time slots while respecting availability and cancellations.
Authorized job feed ingestion
Ingest public authorized job feeds, normalize records and expose original source provenance.
Private resume version storage
Store editable resume versions and owner-controlled export/share snapshots.
Evidence-grounded learning recommendations
Suggest the next practice task from recorded mistakes and explicit goals.
Inventory holds across warehouses
Reserve product quantities during checkout across warehouses.
Parcel tracking events
Ingest parcel scans and display a coherent tracking history to customers.
Video transcoding pipeline
Upload videos and produce multiple playback renditions with status tracking.
Private photo library
Store private photos, generate thumbnails and support shared albums.
Geofence event detection
Notify when a device enters or leaves a configured geographic zone.
Device software update rollouts
Roll out signed device updates with staged cohorts and rollback.
Live competition leaderboard
Rank participants by score and show neighborhood rankings with tie rules.
Versioned API gateway routing
Route requests to services with per-route authentication, timeouts and canary versions.
Distributed task leases
Coordinate workers so a task has one valid lease holder at a time.
Durable scheduled tasks
Run tenant tasks at scheduled times with retries and missed-run policies.
Streaming data transformation
Transform events into curated analytics records with schema evolution.
Tenant analytics warehouse
Provide customer dashboards over tenant-scoped event aggregates.
Stable experiment assignment
Assign users to experiments and record exposure events consistently.
Reliable private data exports
Let users export their own data as a bounded downloadable archive.
Multi-region account failover
Keep account reads/writes available across two regions with a defined recovery policy.
Online schema migration
Migrate a large user table to a new schema while the application keeps writing.
Scoped secret distribution
Deliver credentials to authorized services with rotation and audit history.
Distributed tenant cost budgets
Reserve budgets before paid operations and reconcile actual costs afterward.
Offline note synchronization
Sync learner notes between phone and browser with offline edits and deletion.
Risk event review pipeline
Collect transaction risk signals and queue cases for authorized human review.
Source-grounded learning coach
Answer preparation questions using an approved content library with source references.
Versioned question and test bank
Publish coding questions while keeping grading cases private and preserving old submissions.
Fair scheduling for sandbox jobs
Allocate isolated code-runner workers across competing tenants with deadlines.
Auditable usage metering
Meter API consumption and produce monthly tenant invoices from usage events.
Bounded authorized web crawler
Crawl an explicitly authorized set of public domains with duplicate detection and resource budgets.
One-time verification links
Verify account email with expiring one-time links, resend limits and delivery status.
Evidence-based support case routing
Route incoming support cases to qualified agents while preserving case history.