Amazon Easy DS Problems sorted by frequency

1. Two Sum – HashMap
2. Best Time to Buy and Sell Stock – Arrays
3. Reverse Linked List – Linked List
4. Valid Parentheses – Stack
5. Palindrome Number – Math/String
6. Flood Fill – DFS/BFS on 2D grid
7. Roman to Integer – HashMap
8. Contains Duplicate – Set
9. Invert Binary Tree – Binary Tree (recursion)
10. Move Zeroes – Array (two pointers)
11. First Unique Character in a String – HashMap
12. Fizz Buzz – Basic logic
13. Climbing Stairs – DP/Fibonacci
14. Merge Sorted Array – Two pointers
15. Majority Element – Boyer-Moore / HashMap
16. Valid Anagram – HashMap / Sorting
17. Missing Number – Math/XOR
18. Middle of the Linked List – Linked List
19. Maximum Difference Between Increasing Elements – Array
20. Length of Last Word – String
21. Convert Sorted Array to BST – Binary Tree
22. Pascal’s Triangle – Array
23. Valid Palindrome – Two pointers / String
24. Single Number – XOR
25. Happy Number – Set
26. Palindrome Linked List – Linked List
27. Meeting Rooms – Interval merge
28. Valid Word Abbreviation – String
29. Next Greater Element I – Stack
30. Diameter of Binary Tree – Binary Tree
31. Average of Levels in Binary Tree – Binary Tree (BFS)
32. Search in a BST – Binary Tree
33. Min Cost Climbing Stairs – DP
34. Rotate String – String manipulation
35. Number of Recent Calls – Queue
36. Kth Missing Positive Number – Array
37. Design Parking System – Simulation
38. Sum of Unique Elements – HashMap
39. Recyclable and Low Fat Products – SQL (if applicable)
40. Divisible and Non-divisible Sums Difference – Math
41. Max Difference Between Adjacent Elements in Circular Array – Array

Based on Data Structure Bucket:

Arrays (16)

1. Two Sum
2. Best Time to Buy and Sell Stock
3. Move Zeroes
4. Climbing Stairs
5. Merge Sorted Array
6. Majority Element
7. Missing Number
8. Maximum Difference Between Increasing Elements
9. Length of Last Word
10. Pascal’s Triangle
11. Single Number
12. Next Greater Element I
13. Kth Missing Positive Number
14. Sum of Unique Elements
15. Divisible & Non-divisible Sums Diff
16. Max Diff Between Adjacent Elements (Circular)

Linked Lists (3)

1. Reverse Linked List
2. Middle of the Linked List
3. Palindrome Linked List

Strings (7)

1. Palindrome Number
2. Roman to Integer
3. First Unique Character in a String
4. Valid Anagram
5. Valid Palindrome
6. Valid Word Abbreviation
7. Rotate String

Trees / Binary Tree (5)

1. Invert Binary Tree
2. Convert Sorted Array to BST
3. Diameter of Binary Tree
4. Average of Levels in Binary Tree
5. Search in a BST

Stack (1)

1. Valid Parentheses

Set/Map (2)

1. Contains Duplicate
2. Happy Number

Queue (1)

1. Number of Recent Calls

Simulation (1)

1. Design Parking System

Misc / Logic / Math (5)

1. Fizz Buzz
2. Meeting Rooms
3. Recyclable and Low Fat Products
4. Max Difference Between Adjacent Elements (Circular)
5. Sum of Unique Elements

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