Maximum coins from k consecutive bagsCodingBags stand at every positive integer position. Each segment l, r, v says every bag from l to r holds v; segments don't overlap and all other bags are empty. Choose k consecutive…
Last asked Sep 2026
#prefix sums
Character at an index of a run-length encoded stringCodingA string is stored run-length encoded, like "B1A2E3C1" for BAAEEEC. Return the character at a given index without decoding the string. Follow-up: many queries; precompute prefix…Last asked Sep 2026
Longest all-equal array after merging neighbours into their sumsCodingYou may replace any run of adjacent elements with their sum. Make every element of the resulting array equal while keeping it as long as possible, and return that length. Only the…Last asked Sep 2026- Train fare calculator with a weekend capCodingA train line runs through stations G, U, H, K and I in that order. Each hop between neighbouring stations costs 1, so a trip costs the number of hops it covers (G to I costs 4)…Last asked Aug 2026
+1Count the maximum in each queried suffixCodingYou are given an integer array nums of length n and an array query of 0-based start indices. For each index i in query, look at the suffix numsi, numsi+1, ..., numsn-1. Find the…Last asked Aug 2026
Subarray sum equals kCodingCount the contiguous subarrays whose sum equals k; the array may contain negative numbers. Follow-ups: only report whether such a subarray exists, or return the longest one.Last asked Aug 2026
Two contiguous delivery routes with the most revenueCodingStops along a line each bring some revenue. Pick two contiguous routes (segments of stops) that do not overlap so that their total revenue is as large as possible.Last asked Jul 2026
Count how many rectangles cover each grid cellCodingRectangles are laid on a grid, each one an update that covers a block of cells. Return, for every cell, how many rectangles cover it, without walking every cell of every…Last asked Jul 2026- Weighted random pick with add and removeCoding1. Given positive weights, return a random index with probability proportional to its weight. 2. Turn it into a structure of weighted keys that supports adding a key, removing a…Last asked Jul 2026
+1Random pick weighted by populationCodingGiven countries and their populations, write a picker that returns a random country with probability proportional to its population. Build prefix sums once, draw a random number…Last asked Jul 2026- Shortest delivery route around a ring of hubsCodingDrone hubs sit on a ring, and you know the distance between each hub and its neighbour. The drone visits a list of destination hubs in order, and each leg takes the shorter way…Last asked Jun 2026
- Single-direction stock rebalancing on a ringCodingA company keeps stock in n depots placed around a ring. Depot i is joined to depot (i + 1) % n (the clockwise neighbour) and, through the same link, to depot (i - 1 + n) % n…Last asked Jun 2026
Zero array after range-decrement queriesCodingYou get an array of non-negative integers and a list of queries l, r. Each query lets you subtract 1 from any chosen positions between l and r. Decide whether the array can be all…Last asked Apr 2026- Remove one link and split a gold chain evenlyCodingAn array describes a gold chain; each number is the weight of one link. You must remove one link, join the chain back together, and then cut it into two pieces of equal weight for…Last asked Apr 2026
- Maximum sum of a subarray whose ends differ by kCodingGiven an integer array and k, a subarray is good when its first and last elements differ by exactly k. Return the largest sum of a good subarray, or 0 if there is none.Last asked Apr 2026
- Max purchases from a sorted price rowCodingA market hall has n stalls in a row, numbered 1..n. Stall i sells a single kind of item at price pricesi-1, and the prices are non-decreasing from left to right. A shopper may buy…Last asked Mar 2026
- Range sum query (immutable)CodingPreprocess an integer array so that the sum of any range i, j is answered in constant time. Build prefix sums once and design the function so it can be reused across many queries.Last asked Feb 2026
- Lift-to-stairs switch with an energy budgetCodingYou start on floor 0 of a building with 0 energy and need to reach floor n. You ride the lift from floor 0 up to some floor k (0 <= k <= n), then walk the stairs from floor k to…Last asked Feb 2026
Remaining path length at every waypoint of a batch of trajectoriesCodingYou get a tensor of trajectories of shape batch, numwaypoints, 2 (x, y per waypoint). Return a tensor of shape batch, numwaypoints with a suffix sum for every waypoint: the…Last asked Feb 2026- +2Product of array except selfCodingReturn an array where each position holds the product of every other element, without division and in linear time, using prefix and suffix products; then do it with constant extra…Last asked Feb 2026
- Count subarrays that sum to KCodingGiven an array of integers (negatives allowed) and k, count the contiguous subarrays whose sum is exactly k. Keep running prefix sums and a map from each prefix sum to how often…Last asked Feb 2026
- Sum of all consecutive-step subarraysCodingCall a subarray consecutive when each element is exactly one more than the one before it, or each is exactly one less (a single element counts). Return the sum of the values of…Last asked Feb 2026
- Weighted 01 and 10 subsequence pairs with wildcardsCodingA status string holds '0', '1' and '!'. Every pair of positions i < j that reads 0 then 1 (a subsequence, not a substring) costs x, and every pair that reads 1 then 0 costs y…Last asked Jan 2026
- Range queries: is the subarray parity-alternatingCodingCall an array special when every pair of neighbouring elements has different parity (one odd, one even). Given an integer array and many queries from, to, answer for each query…Last asked Jan 2026
- Weighted random value generatorCodingGiven values with positive weights, write a generator that returns a value at random with probability proportional to its weight. Build it once and answer many calls quickly, and…Last asked Jan 2026
- Most consecutive elements from an index whose sum stays below a targetCodingYou get a non-decreasing array, a start index and a target. Return how many consecutive elements, starting at that index, can be added while the sum stays below the target. Use…Last asked Nov 2025
- Contiguous array with equal 0s and 1sCodingGiven a binary array, return the length of the longest contiguous subarray with as many 0s as 1s. Treat 0 as -1 and look for two equal prefix sums as far apart as possible.Last asked Nov 2025
- Random pick with weightCodingGiven positive weights, implement pick() that returns index i with probability wi / sum(w). Build prefix sums once, then binary search a random number into them. One version gives…Last asked Oct 2025
- Brightest position on a streetCodingEach street lamp has a position and a range, and lights every point within that range on both sides. Return the leftmost position lit by the most lamps.Last asked Sep 2025
- Distance to the nearest waypoint along a routeCodingYou are writing part of a car's navigation software. A route is a polyline: an ordered list of 2D waypoints coordinates, connected by straight segments from each waypoint to the…Last asked Aug 2025
- Subarrays with power-of-two length and sum between K and 2KCodingGiven an integer array and k, find every contiguous subarray whose length is a power of two and whose sum lies between k and 2k. Use prefix sums so each candidate is checked in…Last asked Aug 2025
- Remove k consecutive machines to minimize strength differencesCodingMachines stand in a row, each with a strength. Remove exactly k consecutive machines so that the sum of absolute differences between neighbouring strengths in the remaining row is…Last asked Aug 2025
- Budget queries on a sorted price list, then a shortest pathCodingTwo problems in a 90-minute assessment. First, items come sorted by price; for each budget query, return how many items you can buy. A knapsack DP is too slow; prefix sums with…Last asked Aug 2025
- Car poolingCodingA vehicle with a given capacity drives in one direction. Each trip is passengers, start, end. Return whether all trips fit without ever exceeding capacity, by sorting pickup and…Last asked Aug 2025
- Split an array into two halves with equal sumsCodingYou are given an array nums of positive integers. Find an index i that splits it into two non-empty contiguous parts with the same sum: - the left part is nums0..i (it includes…
- Split a string into blocks that match the prefix's letter countsCodingYou get a string s of uppercase letters A-Z. Call a positive length L valid when: - L <= len(s) and s can be cut into consecutive, non-overlapping blocks of exactly L characters…
- Minimum starting battery for a task queueCodingA server runs a queue of jobs strictly in order, powered by one battery. Job i changes the battery by -usagei: a positive usagei drains the battery, and a negative one means the…
- Best k-day run in a cyclic sprint scheduleCodingA training program is made of n back-to-back sprints. Sprint i lasts daysi days. On day j of a sprint (counting from 1 within that sprint), finishing that day's work earns j…
- Levels cleared from every starting pointCodingA game has n levels in a row. You are given two integer arrays of length n, layers and energy, and an integer K. A run that starts at level i begins with exactly K energy and…
- Garage occupancy at every timestampCodingA parking garage records occupancy over n discrete timestamps, numbered 0 to n - 1. You get a list of parking tickets. Ticket entry, exit means one car arrived at timestamp entry…
- Best starting layer for a falling ball with an energy budgetCodingA ball falls through a tower of n layers, numbered 0 (top) to n - 1 (bottom). You get two integer arrays of length n and one integer: - costsi (= 0): the energy the ball spends to…
- Count redundant substrings by vowel and consonant weightsCodingWrite a function that counts the redundant substrings of a word. A string s is redundant when its length equals a V + b C, where V is the number of vowels in s, C is the number of…
- Longest run of customers a bank can serveCodingA bank opens with initial dollars in its vault (initial = 0). Customers wait in a fixed queue, given as an integer array transactions: a positive value is a deposit and a negative…
Cross the most walls on a number line with limited energyCodingWalls stand at distinct non-zero integer points on an infinite number line. Wall k is at positionsk and costs costsk = 0 energy to cross. You start at 0 with energy units. Each…- Count stable server segmentsCodingA row of n machines has integer capacities capacity0..n-1. A contiguous segment l, r is stable when all of these hold: 1. It contains at least 3 machines (r - l = 2). 2. The two…