17 Letter Combinations of a Phone Number

22 Generate Parentheses

37 Sudoku Solver

39 Combination Sum

40 Combination Sum II

44 Wildcard Matching

46 Permutations

47 Permutations II

51 N-Queens

52 N-Queens II

60 Permutation Sequence

77 Combinations

78 Subsets

79 Word Search

89 Gray Code

90 Subsets II

93 Restore IP Addresses

131 Palindrome Partitioning

212 Word Search II

216 Combination Sum III

254 Factor Combinations

267 Palindrome Permutation II

291 Word Pattern II

320 Generalized Abbreviation

351 Android Unlock Patterns

357 Count Numbers with Unique Digits

401 Binary Watch

411 Minimum Unique Word Abbreviation

425 Word Squares

473 Matchsticks to Square

491 Increasing Subsequences

526 Beautiful Arrangement

679 24 Game

691 Stickers to Spell Word

797 All Paths From Source to Target