Prefix Sums coding problems

Prefix sums answer range questions in O(1) after one pass. Practise subarray sums, equal-sum splits, counting subarrays with a target sum and 2D range totals.

64 problems: 14 easy, 43 medium, 7 hard. Free to read; a free account solves them and earns XP and Aura.

1. Alternating Prefix SumsPractice · +10 XP · prefix sums, array manipulationeasy
2. Alternating SumPractice · +10 XP · prefix sums, loops, basic arithmeticeasy
3. Count Non-Negative SubarraysPractice · +10 XP · sliding window, prefix sums, arrayseasy
4. Count Subarrays with Target SumPractice · +10 XP · sliding window, prefix sums, hash mapeasy
5. Cumulative Array SumPractice · +10 XP · prefix sums, range querieseasy
6. Cumulative DifferencesPractice · +10 XP · prefix sums, difference arrayseasy
7. Cumulative Sum of DifferencesPractice · +10 XP · prefix sums, difference arrays, range querieseasy
8. Max Element in PrefixPractice · +10 XP · stack, prefix sums, arrayseasy
9. Maximum Sum of a Fixed-Size SubarrayPractice · +10 XP · sliding window, arrays, prefix sumseasy
10. Prefix Sum ArrayPractice · +10 XP · prefix sums, range querieseasy
11. Range Sum of DifferencesPractice · +10 XP · prefix sums, range querieseasy
12. Range Sum QueryPractice · +10 XP · prefix sums, range querieseasy
13. Sum of Even-Indexed ElementsPractice · +10 XP · prefix sums, array manipulation, basic programmingeasy
14. Sum of Prefix ProductsPractice · +10 XP · dynamic programming, prefix sumseasy
15. Array Prefix Maxima and MinimaPractice · +20 XP · arrays, prefix sums, running max/minmedium
16. Count Distinct Prefix SumsPractice · +20 XP · math, prefix sums, hashingmedium
17. Count Pairs with Digit Sum Divisible by KPractice · +20 XP · math, hashing, prefix sumsmedium
18. Count Pairs with Equal XOR SumPractice · +20 XP · recursion, prefix sums, hash mapsmedium
19. Count Subarrays with Equal Prefix SumsPractice · +20 XP · prefix sums, hash map, countingmedium
20. Count Subarrays with Target Sum DifferencePractice · +20 XP · prefix sums, hash map, subarray sumsmedium
21. Count XOR PairsPractice · +20 XP · bit manipulation, hash map, prefix sumsmedium
22. Distinct Elements in PrefixPractice · +20 XP · arrays, hash set, prefix sumsmedium
23. Distinct Subgrid ValuesPractice · +20 XP · matrix, prefix sums, hash setmedium
24. Distinct XOR Prefix SumsPractice · +20 XP · bit manipulation, prefix sums, hash setmedium
25. Longest Prefix with Equal CountsPractice · +20 XP · stack, hash map, prefix summedium
26. Longest Subarray with Equal HalvesPractice · +20 XP · sliding window, prefix sums, hash mapmedium
27. Longest Subarray with Sum at Most KPractice · +20 XP · sliding window, prefix sums, two pointersmedium
28. Longest Subarray With Sum XPractice · +20 XP · sliding window, prefix sums, hash mapmedium
29. Matrix Zero Sum SubgridsPractice · +20 XP · matrix, prefix sums, hash mapmedium
30. Max Difference Between Two Prefix SumsPractice · +20 XP · prefix sums, range queries, arraysmedium
31. Maximum Average SubsegmentPractice · +20 XP · binary search, prefix sums, arraysmedium
32. Maximum Depth Sum of Unique PathsPractice · +20 XP · trees, bfs, prefix summedium
33. Maximum Prefix Sum DifferencePractice · +20 XP · prefix sums, array, maximummedium
34. Maximum Rectangle SumPractice · +20 XP · matrix, prefix sums, kadane's algorithmmedium
35. Maximum Subarray Sum with Fixed LengthPractice · +20 XP · queue, sliding window, prefix summedium
36. Maximum Sum of Non-overlapping SubarraysPractice · +20 XP · greedy, dynamic programming, prefix sumsmedium
37. Maximum Sum of PairsPractice · +20 XP · dynamic programming, prefix sums, binary searchmedium
38. Maximum Sum SubmatrixPractice · +20 XP · matrix, prefix sumsmedium
39. Minimum XOR Sum of SubarraysPractice · +20 XP · bit manipulation, prefix sums, hash mapmedium
40. Optimal Training ScheduleOpen now · Weekly · +40 XP · +15 Aura · two pointers, sliding window, prefix sum1 solvedmedium
41. Sort by Subsequence SumPractice · +20 XP · sorting, hash map, prefix summedium
42. String PartitionPractice · +20 XP · strings, hashing, prefix sumsmedium
43. Subarray Digit SumsPractice · +20 XP · math, prefix sums, arraysmedium
44. Subarray Sum and CountPractice · +20 XP · prefix sums, hash map, range queriesmedium
45. Subarray Sum Closest to TargetPractice · +20 XP · prefix sums, binary search, range queriesmedium
46. Subarray Sum FrequenciesPractice · +20 XP · prefix sums, hash map, subarray sumsmedium
47. Subarray Sum MultiplesPractice · +20 XP · prefix sums, hash maps, number theorymedium
48. Subarray Sum RangePractice · +20 XP · stack, monotonic stack, prefix summedium
49. Subarray Sums with Target DifferencePractice · +20 XP · prefix sums, hash maps, countingmedium
50. Subarray XOR with TargetPractice · +20 XP · bit manipulation, hash map, prefix summedium
51. Subsegment Sum Divisible by KPractice · +20 XP · recursion, prefix sums, hashingmedium
52. Substring ParityPractice · +20 XP · strings, prefix sums, paritymedium
53. Sum of Minimums of All SubarraysPractice · +20 XP · stack, monotonic stack, prefix summedium
54. Sum of Two Adjacent ElementsPractice · +20 XP · recursion, sliding window, prefix summedium
55. Tree Ancestor SumPractice · +20 XP · trees, prefix sums, traversalsmedium
56. XOR Pairs with Zero SumPractice · +20 XP · bit manipulation, hash map, prefix sumsmedium
57. XOR Sequence PartitionPractice · +20 XP · bit manipulation, hash map, prefix sumsmedium
58. Bitwise OR Subarray SumPractice · +30 XP · bit manipulation, prefix sums, data structureshard
59. Longest Balanced SubarrayPractice · +30 XP · arrays, hash maps, prefix sumshard
60. Longest Subarray with Equal Number of Zeroes and OnesPractice · +30 XP · two pointers, prefix sum, hash maphard
61. Minimize Maximum Difference of Grouped ElementsPractice · +30 XP · binary search, greedy, prefix sumshard
62. Minimum Cost Subarray with Sum at Least KPractice · +30 XP · sliding window, prefix sums, monotonic queuehard
63. Prefix Sums and ParityPractice · +30 XP · prefix sums, parity, combinatoricshard
64. Subarray Minimums with SumPractice · +30 XP · arrays, monotonic stack, prefix sumshard