1. Find the longest substring that contains at most k characters that are not vowels.
2. Implement a function to find the longest subarray with at most k distinct integers.
3. Given a sorted array, find the minimum difference between any two elements.
4. Count the number of ways to partition an array into two subsets such that the sum of each subset is equal.
5. Find the longest increasing subsequence of a string considering only alphabetical characters.
6. Determine the maximum length of a subarray that sums to zero.
7. Given a string, find the longest palindromic substring that can be obtained by removing at most k characters.
8. Check if two strings are permutations of each other by character frequency.
9. Find the longest substring of a string that contains at most one repeating character.
10. Determine the maximum product of a subarray of size k.
11. Check if a binary tree is a valid BST using the two-pointer technique.
12. Count the number of subarrays that satisfy the condition of being divisible by a given number.
13. Find the smallest window in a string that contains all characters of another string.
14. Determine if there exists a continuous subarray of size at least k whose sum is equal to a given number.
15. Check if a string can be formed by rearranging characters of another string with at least one character difference.
16. Find the longest sequence of non-decreasing integers in an array.
17. Count the number of distinct triplets in an array that sum to a target value.
18. Implement a function to find the minimum number of characters to delete to make two strings anagrams of each other.
19. Given a circular linked list, determine if it has a cycle using two pointers.
20. Find the maximum area of a rectangle in a histogram using the two-pointer technique.
21. Calculate the number of valid combinations of brackets using a two-pointer approach.
22. Determine if two strings can be made equal by swapping two characters.
23. Find the longest subsequence that can be formed from two strings with at most one edit distance.
24. Given an array of integers, find the maximum product of any three integers.
25. Check if a sequence of numbers can form a geometric progression.
26. Count the number of palindromic substrings in a string using dynamic programming and two pointers.
27. Find the longest substring that contains all unique characters and a minimum length.
28. Implement a function to find the intersection of two linked lists.
29. Count the number of substrings that contain at least one character c.
30. Given a 2D matrix, find the maximum sum of any subarray using the two-pointer approach.
31. Check if a string can be rearranged to form a valid palindrome using character frequency.
32. Find the maximum length of a substring that contains at most two types of characters.
33. Determine the maximum length of a sequence of distinct integers in a circular array.
34. Calculate the number of valid configurations of parentheses for n pairs.
35. Find the maximum number of pairs that sum to a specific target value in an array.
36. Given a string, check if it can be transformed into another string by a series of swaps.
37. Implement a function to find the longest valid parentheses substring using the two-pointer technique.
38. Count the number of unique paths in a grid with obstacles.
39. Given a string, find the number of substrings that contain at least one of each vowel.
40. Check if an array can be sorted with at most one swap.