Representative Prefix Sum problems
Find the minimal length of a subarray whose sum is greater than or equal to the target using efficient algorithms.
Open problem page#238 Product of Array Except SelfSolve the 'Product of Array Except Self' problem by calculating the product of all elements except self for each index efficiently.
Open problem page#303 Range Sum Query - ImmutableThe Range Sum Query - Immutable problem involves implementing a data structure to handle range sum queries efficiently.
Open problem page#304 Range Sum Query 2D - ImmutableDesign a 2D matrix class that efficiently handles sum queries with O(1) time complexity using a prefix sum approach.
Open problem page#363 Max Sum of Rectangle No Larger Than KSolve the "Max Sum of Rectangle No Larger Than K" problem using binary search over the valid sum space to optimize space and time complexity.
Open problem page#410 Split Array Largest SumSolve the 'Split Array Largest Sum' problem by minimizing the largest sum across k subarrays using dynamic programming and binary search.
Open problem page#497 Random Point in Non-overlapping RectanglesDesign an algorithm to pick random points within non-overlapping rectangles using binary search and reservoir sampling.
Open problem page#523 Continuous Subarray SumIdentify if any continuous subarray sums to a multiple of k using prefix sums and hash table tracking efficiently.
Open problem page#525 Contiguous ArrayFind the maximum length contiguous subarray with equal numbers of 0s and 1s using array scanning and hash lookup efficiently.
Open problem pagePrefix Sum interview questions usually collapse into a small set of repeatable moves. This page groups those GhostInterview problem pages together so you can stay inside one pattern family, compare representative questions, and practice explanations that transfer across multiple prompts. If you are trying to sharpen one interview weakness instead of browsing the entire library, start here.
Why Prefix Sum Matters In Coding Interviews
Interviewers rarely care about the label alone. They care about whether you can recognize when the Prefix Sum pattern applies, explain why it applies, and avoid the failure modes that usually show up under time pressure. That is why this page focuses on the family of problems rather than a single isolated example.
Pattern families that show up here
- Binary search over the valid answer space
- Array scanning plus hash lookup
- State transition dynamic programming
Use this page to narrow the session
Start from this topic hub, choose one or two representative problems, and then open the detailed problem pages only after you know which version of the pattern you want to reinforce.
How To Practice This Topic
The best workflow is to keep the prep block narrow. Pick one easy or medium problem to confirm the base pattern, then one medium or hard problem to test whether the explanation still holds when the constraints tighten. Once the logic is stable, move into GhostInterview to rehearse the live explanation flow.
Focus on transfer, not title count
Solving more Prefix Sum titles is less useful than understanding how the same move changes across examples. Try to describe what stays the same and what changes from one problem to the next.
Use the problem page when you want the exact breakdown
This topic hub is the discovery layer. The single-problem pages are where you get the answer-first summary, examples, constraints, approach, complexity, pitfalls, and solver CTA.
How GhostInterview Fits
GhostInterview works best after you know which pattern family you are inside. Use this page to choose the right Prefix Sum problem, then use the solver to get the answer path, complexity framing, and follow-up support without switching into a generic study flow.
FAQ
What does the Prefix Sum topic usually test in interviews?
Prefix Sum questions usually test whether you can spot the underlying pattern quickly, explain the trade-offs, and move from intuition to implementation without losing clarity.
How should I use this Prefix Sum topic page?
Use it as a pattern hub. Start with the representative problems on this page, compare the common approach, and then open the exact problem page when you want the full breakdown.
How many GhostInterview problem pages are in the Prefix Sum group?
This topic page currently groups 186 indexed GhostInterview problem pages under the Prefix Sum family.
Should I practice this topic before harder patterns?
That depends on your current gaps. If Prefix Sum is already a weak spot in interviews, it is usually better to stabilize it first before moving into more advanced or less frequent patterns.
Where does GhostInterview fit once I pick a Prefix Sum problem?
The topic page narrows the pattern family. The problem page gives the exact breakdown. GhostInterview is the solver layer when you need direct help with execution, complexity, and follow-up handling.
Stay close to the same reasoning family
1,672 overlapping problems
Open topic pageBinary Search265 overlapping problems
Open topic pageHash Table610 overlapping problems
Open topic pageDynamic Programming529 overlapping problems
Open topic pageSliding Window133 overlapping problems
Open topic pageString699 overlapping problems
Open topic pageNeed direct help once you choose a Prefix Sum problem?
Use GhostInterview as the solver layer after you select the exact prompt. Capture the question, get the answer path and complexity framing, and keep the workflow inside the same topic family.