1. Generate all permutations of a given string.
2. Solve the N-Queens problem.
3. Find all subsets of a given set.
4. Solve the Sudoku puzzle.
5. Generate all combinations of a given set of numbers.
6. Solve the maze problem with obstacles.
7. Generate all valid parentheses combinations for n pairs.
8. Find all unique permutations of a list with duplicates.
9. Solve the word search problem in a grid.
10. Generate all possible ways to place knights on a chessboard.
11. Find all Hamiltonian paths in a graph.
12. Solve the K-sum problem using backtracking.
13. Generate all combinations of a string with repeated characters.
14. Solve the problem of placing rooks on a chessboard.
15. Generate all valid IP addresses from a string of digits.
16. Solve the problem of word breaks in a string.
17. Find all unique combinations of numbers that sum to a target.
18. Generate all arrangements of a list of tasks with dependencies.
19. Solve the problem of partitioning a string into palindromic substrings.
20. Generate all possible subsets of a list of numbers.
21. Solve the problem of generating all valid combinations of brackets.
22. Find all distinct subsequences of a string.
23. Generate all combinations of coins to make change for a target value.
24. Solve the problem of placing queens on a chessboard without attacking each other.
25. Find all unique paths in a grid from the top left to bottom right.
26. Generate all possible ways to arrange a list of books on a shelf.
27. Solve the problem of generating all possible paths in a directed acyclic graph.
28. Find all valid combinations of digits to form a specific target number.
29. Generate all possible assignments of tasks to workers.
30. Solve the problem of generating all valid combinations of substrings from a string.
31. Find all combinations of numbers that can form a valid triangle.
32. Generate all distinct combinations of coins to make change.
33. Solve the problem of generating all unique combinations of letters in a word.
34. Find all unique arrangements of a set of objects.
35. Generate all possible sequences of moves in a grid.
36. Solve the problem of generating all valid paths in a maze.
37. Find all combinations of items that fit into a knapsack.
38. Generate all valid configurations of a chessboard.
39. Solve the problem of generating all valid assignments of colors to a graph.
40. Find all combinations of digits that form a valid phone number.