Array Problems

1. Two Sum: Find two numbers that add up to a target
2. Running Sum of Array: Calculate cumulative sum
3. Remove Duplicates from Sorted Array
4. Remove Element from Array
5. Search Insert Position: Find index where element should be inserted
6. Find First and Last Position of Element in Sorted Array
7. Merge Sorted Arrays
8. Maximum Subarray Sum
9. Move Zeroes to End
10. Contains Duplicate
11. Single Number: Find element that appears once
12. Intersection of Two Arrays
13. Plus One: Increment array of digits representing integer
14. Rotate Array by K positions
15. Find Peak Element in Array
16. Find Missing Number in Array
17. Majority Element: Find element appearing more than n/2 times
18. 3Sum: Find three elements that sum to zero
19. Product of Array Except Self
20. Kth Largest Element in Array

String Problems

21. Two String Anagram Check
22. Remove Duplicates from String
23. Reverse Words in String
24. Valid Palindrome
25. Longest Common Prefix
26. String to Integer (atoi)
27. Count and Say Sequence
28. Implement strStr(): Find first occurrence of substring
29. Longest Substring Without Repeating Characters
30. Valid Parentheses
31. Group Anagrams
32. Longest Palindromic Substring
33. String Compression
34. Reverse String in Place
35. Validate IP Address
36. Regular Expression Matching

Linked List Problems

37. Reverse Linked List
38. Detect Cycle in Linked List
39. Merge Two Sorted Lists
40. Remove Nth Node From End of List
41. Delete Node in Linked List
42. Palindrome Linked List
43. Middle of Linked List
44. Swap Nodes in Pairs
45. Linked List Cycle II: Find start of cycle
46. Intersection of Two Linked Lists

Stack and Queue Problems

47. Implement Stack using Queues
48. Implement Queue using Stacks
49. Min Stack: Design stack with constant-time getMin()
50. Evaluate Reverse Polish Notation
51. Daily Temperatures: Find days until warmer temperature
52. Next Greater Element
53. Valid Parenthesis String
54. Implement Circular Queue

Tree Problems

55. Binary Tree Level Order Traversal
56. Maximum Depth of Binary Tree
57. Validate Binary Search Tree
58. Symmetric Tree
59. Path Sum in Binary Tree
60. Lowest Common Ancestor of Binary Tree
61. Binary Tree Zigzag Level Order Traversal
62. Convert Sorted Array to Binary Search Tree
63. Serialize and Deserialize Binary Tree
64. Flatten Binary Tree to Linked List

Graph Problems

65. Number of Islands
66. Course Schedule (Detect Cycle in Directed Graph)
67. Clone Graph
68. Word Ladder: Transform word to another changing one letter
69. Flood Fill
70. Pacific Atlantic Water Flow
71. Network Delay Time
72. Find the Town Judge

Dynamic Programming Problems

73. Climbing Stairs
74. Coin Change
75. Longest Increasing Subsequence
76. Edit Distance
77. Unique Paths
78. House Robber
79. Maximum Product Subarray
80. Word Break
81. Decode Ways
82. Minimum Path Sum

Test Automation Specific Problems

83. Parse and Validate CSV File
84. Implement Page Object Model Framework
85. Design Data-Driven Test Framework
86. Implement Custom Wait Mechanism
87. Create a Test Report Generator
88. Implement Retry Logic for Flaky Tests
89. Extract Data from API Response
90. Design Pattern for Test Data Management
91. Implement Screenshot Capture on Test Failure
92. Create Element Highlighter for Debugging

Concurrency and Threading Problems

93. Producer-Consumer Problem Implementation
94. Thread-Safe Singleton Pattern
95. Parallel Test Execution Framework
96. Thread Pool Implementation
97. Race Condition Detection Tool

System Design Problems

98. Design a Throttling System for API Tests
99. Design a Distributed Test Execution Framework
100. Design a Self-Healing Test Automation Framework

These problems cover fundamental programming skills, data structures, algorithms, and test automation-specific challenges that would prepare you well for an SDET interview.