38 STACKS AND QUEUES INTERVIEW QUESTIONS

Certainly! Here are the most important 38 stacks and queues interview questions:

1. Implement Stack from Scratch
2. Implement Queue from Scratch
3. Implement 2 stacks in an array
4. Find the middle element of a stack
5. Check if the expression has valid or balanced parenthesis or not.
6. Reverse a String using Stack
7. Design a Stack that supports getMin() in O(1) time and O(1) extra space.
8. Find the next Greater element
9. The celebrity Problem
10. Arithmetic Expression evaluation
11. Evaluation of Postfix expression
12. Implement a method to insert an element at its bottom without using any other data structure.
13. Reverse a stack using recursion
14. Sort a Stack using recursion
15. Merge Overlapping Intervals
16. Largest rectangular Area in Histogram
17. Length of the Longest Valid Substring
18. Expression contains redundant bracket or not
19. Implement Stack using Queue
20. Implement Stack using Deque
21. Stack Permutations (Check if an array is a stack permutation of the other)
22. Implement Queue using Stack
23. Implement "n" queues in an array
24. Implement a Circular queue
25. LRU Cache Implementation
26. Reverse a Queue using recursion
27. Reverse the first "K" elements of a queue
28. Interleave the first half of the queue with the second half
29. Find the first circular tour that visits all Petrol Pumps
30. Minimum time required to rot all oranges
31. Distance of the nearest cell having 1 in a binary matrix
32. First negative integer in every window of size "k"
33. Check if all levels of two trees are anagrams or not.
34. Sum of minimum and maximum elements of all subarrays of size "k".
35. Minimum sum of squares of character counts in a given string after removing "k" characters.
36. Queue-based approach for the first non-repeating character in a stream.
37. Next Smaller Element
38. Implement "N" stacks in an Array