1. Write a recursive function to solve the N-Queens problem.
2. Write a recursive function to find all permutations of a string.
3. Write a recursive function to generate all combinations of k elements from n elements.
4. Write a recursive function to find all subsets of a set (power set).
5. Write a recursive function to solve the Tower of Hanoi problem.
6. Write a recursive function to evaluate a mathematical expression given in reverse Polish notation.
7. Write a recursive function to find the shortest path in a weighted graph using Dijkstra's algorithm.
8. Write a recursive function to solve the subset sum problem.
9. Write a recursive function to count the number of valid parentheses combinations of length n.
10. Write a recursive function to generate all possible expressions from a given list of numbers and operators to achieve a target value.
11. Write a recursive function to find the longest common subsequence of two strings using memoization.
12. Write a recursive function to find the nth Catalan number.
13. Write a recursive function to solve the coin change problem for an unlimited supply of coins.
14. Write a recursive function to find all unique permutations of a list that may contain duplicates.
15. Write a recursive function to generate the combinations of all elements in a list with repetition allowed.
16. Write a recursive function to find the number of ways to arrange n distinct objects in a line.
17. Write a recursive function to generate all possible configurations of a given number of knights on a chessboard.
18. Write a recursive function to determine if two strings are anagrams of each other.
19. Write a recursive function to find the longest path in a grid that allows diagonal moves.
20. Write a recursive function to find all Hamiltonian paths in a graph.
21. Write a recursive function to find the maximum sum of non-adjacent elements in an array.
22. Write a recursive function to find the number of ways to tile a 2 x n rectangle using 1 x 2 dominoes.
23. Write a recursive function to generate all possible combinations of a given size from a list with repetitions allowed.
24. Write a recursive function to determine if a given Sudoku board is valid.
25. Write a recursive function to find the number of ways to make change for a specific amount using a list of denominations.
26. Write a recursive function to find the longest increasing subsequence in an array.
27. Write a recursive function to find the maximum sum path in a triangle of numbers.
28. Write a recursive function to find all possible paths in a maze with obstacles.
29. Write a recursive function to solve the knapsack problem with fractional weights.
30. Write a recursive function to generate the sequence of Fibonacci numbers using matrix exponentiation.
31. Write a recursive function to find the maximum product of any two numbers in an array.
32. Write a recursive function to check if a string can be segmented into words from a given dictionary.
33. Write a recursive function to find the number of unique ways to climb stairs where you can take 1, 2, or 3 steps.
34. Write a recursive function to generate all valid IP addresses from a string of digits.
35. Write a recursive function to find the minimum number of edits needed to convert one string into another (Levenshtein distance).
36. Write a recursive function to find the longest substring with at most k distinct characters.
37. Write a recursive function to solve the problem of placing N bishops on an N x N chessboard such that no two bishops attack each other.
38. Write a recursive function to find the longest palindromic subsequence in a string.
39. Write a recursive function to find the sum of all subsets of a given set.
40. Write a recursive function to count the number of ways to partition a set into two subsets with equal sum.