Arrays

Traversal, prefix sums, two pointers and sliding windows.

84 problems

Title	Tags	Acceptance	Difficulty
1. Sum of Array	Array	—	Easy
2. Minimum and Maximum	Array	—	Easy
3. Reverse an Array	Array · Two Pointers	—	Easy
4. Second Largest Distinct Element	Array	—	Easy
5. Count Even and Odd	Array	—	Easy
6. Prefix Sums	Array · Prefix Sum	—	Easy
7. Range Sum Queries	Prefix Sum	—	Medium
8. Left Rotation	Array	—	Easy
9. Remove Duplicates from Sorted Array	Two Pointers	—	Easy
10. Merge Two Sorted Arrays	Two Pointers · Merge	—	Easy
11. Negatives Before Positives	Array · Partition	—	Easy
12. Leaders in an Array	Array · Suffix Max	—	Easy
13. Equilibrium Index	Prefix Sum	—	Medium
14. Max Consecutive Ones	Array	—	Easy
15. Missing and Repeating	Array · Math	—	Medium
16. Best Subarray with Bounds	Kadane	—	Medium
17. Product Modulo	Modular Arithmetic	—	Easy
18. Pair with Given Difference	Hash Set	—	Medium
19. Count Pairs with Sum	Hash Map · Counting	—	Medium
20. Subarrays with Sum K	Prefix Sum · Hash Map	—	Medium
21. Longest Subarray with Sum K	Prefix Sum · Hash Map	—	Medium
22. Maximum Sum Window	Sliding Window	—	Easy
23. Shortest Subarray with Sum ≥ S	Sliding Window · Two Pointers	—	Medium
24. Count Inversions	Merge Sort · Divide and Conquer	—	Hard
25. Elements More Than n/3 Times	Counting	—	Medium
26. Stock Span	Monotonic Stack	—	Medium
27. Sort 0s, 1s and 2s	Dutch National Flag	—	Easy
28. Next Permutation	Permutation	—	Medium
29. Alternate Positive and Negative	Array	—	Medium
30. Find a Peak Element	Binary Search	—	Medium
31. Intersection of Two Arrays	Set	—	Easy
32. Union of Two Arrays	Set	—	Easy
33. Sort by Frequency	Sorting · Hash Map	—	Medium
34. First Repeating Element	Hash Map	—	Easy
35. Zig-Zag Arrangement	Greedy	—	Medium
36. Minimum Platforms	Sorting · Sweep Line	—	Medium
37. Chocolate Distribution	Sorting · Sliding Window	—	Easy
38. Maximum Product of Two	Array	—	Easy
39. Distinct Elements in Every Window	Sliding Window · Hash Map	—	Medium
40. Zero-Sum Subarray Exists?	Prefix Sum · Hash Set	—	Easy
41. Maximum Product Subarray	Dynamic Programming	—	Medium
42. Sub-matrix Sum Queries	2-D Prefix Sum	—	Medium
43. Container With Most Water	Two Pointers	—	Medium
44. Two Sum II (Sorted Input)	Two Pointers	—	Medium
45. 3Sum Closest	Two Pointers · Sorting	—	Medium
46. Remove Element	Two Pointers	—	Easy
47. Squares of a Sorted Array	Two Pointers	—	Easy
48. Longest Mountain	Two Pointers · DP	—	Medium
49. Windows With Average ≥ Threshold	Sliding Window	—	Medium
50. Max Consecutive Ones With K Flips	Sliding Window	—	Medium
51. Fruit Into Baskets	Sliding Window · Hash Map	—	Medium
52. Subarray Product Less Than K	Sliding Window	—	Medium
53. Subarrays With Exactly K Odd Numbers	Prefix Sum · Hash Map	—	Medium
54. Binary Subarrays With Sum	Prefix Sum	—	Medium
55. Grumpy Bookstore Owner	Sliding Window	—	Medium
56. Maximum Points From Cards	Sliding Window · Prefix Sum	—	Medium
57. Subarray Sums Divisible by K	Prefix Sum · Modulo	—	Medium
58. Longest Equal 0s and 1s	Prefix Sum · Hash Map	—	Medium
59. Longest Ones After Deleting One Element	Sliding Window	—	Medium
60. Insert Interval	Intervals	—	Medium
61. Interval List Intersections	Intervals · Two Pointers	—	Medium
62. Can Attend All Meetings	Intervals · Sorting	—	Easy
63. Summary Ranges	Array	—	Easy
64. Missing Ranges	Array	—	Easy
65. Find All Duplicates	Array	—	Medium
66. First Missing Positive	Array · Cyclic Sort	—	Hard
67. Find All Missing Numbers	Array	—	Easy
68. Sort Array by Parity (Stable)	Array	—	Easy
69. Relative Sort Array	Counting Sort	—	Easy
70. H-Index	Sorting	—	Medium
71. Range Updates With a Difference Array	Prefix Sum	—	Medium
72. Car Pooling	Prefix Sum · Simulation	—	Medium
73. Corporate Flight Bookings	Prefix Sum	—	Medium
74. Valid Triangle Number	Two Pointers · Sorting	—	Medium
75. Minimum Moves to Equal Elements	Math	—	Medium
76. Longest Harmonious Subsequence	Hash Map	—	Easy
77. Degree of an Array	Hash Map	—	Easy
78. Number of Good Pairs	Counting	—	Easy
79. Kids With the Greatest Number of Candies	Array	—	Easy
80. Shuffle the Array	Array	—	Easy
81. How Many Numbers Are Smaller	Counting Sort	—	Easy
82. Poison Duration	Simulation	—	Easy
83. Distribute Candies	Hash Set	—	Easy
84. Richest Customer Wealth	Matrix	—	Easy

84 of 84 problems