Backtracking LeetCode Problems: All 105, With Python Solutions
Every problem in this library that LeetCode tags Backtracking — 105 in total, 86 of them with a complete Python solution, a worked example and the time and space complexity of the approach.
- 105 problems
- 3 Easy
- 71 Medium
- 31 Hard
How Backtracking problems are solved
A tag names the subject, not the method. These pattern hubs cover the techniques that actually solve Backtracking problems — each one explains the approach, gives a Python template and states its complexity.
- Backtracking — Build candidates one choice at a time and abandon a branch the moment it cannot work.
Backtracking problems by difficulty
Problems with a complete Python solution are listed first, then by ascending problem number.
Easy (3)
| # | Problem | Difficulty | Topics |
|---|---|---|---|
| 257 | Binary Tree Paths | Easy | Tree, Depth-First Search, String +2 |
| 401 | Binary Watch | Easy | Bit Manipulation, Backtracking |
| 1863 | Sum of All Subset XOR Totals | Easy | Bit Manipulation, Array, Math +3 |
Medium (71)
| # | Problem | Difficulty | Topics |
|---|---|---|---|
| 17 | Letter Combinations of a Phone Number | Medium | Hash Table, String, Backtracking |
| 22 | Generate Parentheses | Medium | String, Dynamic Programming, Backtracking |
| 39 | Combination Sum | Medium | Array, Backtracking |
| 40 | Combination Sum II | Medium | Array, Backtracking |
| 46 | Permutations | Medium | Array, Backtracking |
| 47 | Permutations II | Medium | Array, Backtracking, Sorting |
| 77 | Combinations | Medium | Backtracking |
| 78 | Subsets | Medium | Bit Manipulation, Array, Backtracking |
| 79 | Word Search | Medium | Depth-First Search, Array, String +2 |
| 89 | Gray Code | Medium | Bit Manipulation, Math, Backtracking |
| 90 | Subsets II | Medium | Bit Manipulation, Array, Backtracking |
| 93 | Restore IP Addresses | Medium | String, Backtracking |
| 95 | Unique Binary Search Trees II | Medium | Tree, Binary Search Tree, Dynamic Programming +2 |
| 113 | Path Sum II | Medium | Tree, Depth-First Search, Backtracking +1 |
| 131 | Palindrome Partitioning | Medium | String, Dynamic Programming, Backtracking |
| 216 | Combination Sum III | Medium | Array, Backtracking |
| 306 | Additive Number | Medium | String, Backtracking |
| 357 | Count Numbers with Unique Digits | Medium | Math, Dynamic Programming, Backtracking |
| 473 | Matchsticks to Square | Medium | Bit Manipulation, Array, Dynamic Programming +2 |
| 491 | Non-decreasing Subsequences | Medium | Bit Manipulation, Array, Hash Table +1 |
| 494 | Target Sum | Medium | Array, Dynamic Programming, Backtracking |
| 526 | Beautiful Arrangement | Medium | Bit Manipulation, Array, Dynamic Programming +2 |
| 638 | Shopping Offers | Medium | Bit Manipulation, Memoization, Array +3 |
| 698 | Partition to K Equal Sum Subsets | Medium | Bit Manipulation, Memoization, Array +3 |
| 756 | Pyramid Transition Matrix | Medium | Bit Manipulation, Hash Table, String +1 |
| 784 | Letter Case Permutation | Medium | Bit Manipulation, String, Backtracking |
| 797 | All Paths From Source to Target | Medium | Depth-First Search, Breadth-First Search, Graph +1 |
| 816 | Ambiguous Coordinates | Medium | String, Backtracking, Enumeration |
| 842 | Split Array into Fibonacci Sequence | Medium | String, Backtracking |
| 949 | Largest Time for Given Digits | Medium | Array, String, Backtracking +1 |
| 967 | Numbers With Same Consecutive Differences | Medium | Breadth-First Search, Backtracking |
| 988 | Smallest String Starting From Leaf | Medium | Tree, Depth-First Search, String +2 |
| 1079 | Letter Tile Possibilities | Medium | Hash Table, String, Backtracking +1 |
| 1219 | Path with Maximum Gold | Medium | Array, Backtracking, Matrix |
| 1238 | Circular Permutation in Binary Representation | Medium | Bit Manipulation, Math, Backtracking |
| 1239 | Maximum Length of a Concatenated String with Unique Characters | Medium | Bit Manipulation, Array, String +1 |
| 1286 | Iterator for Combination | Medium | Design, String, Backtracking +1 |
| 1415 | The k-th Lexicographical String of All Happy Strings of Length n | Medium | String, Backtracking |
| 1593 | Split a String Into the Max Number of Unique Substrings | Medium | Hash Table, String, Backtracking |
| 1718 | Construct the Lexicographically Largest Valid Sequence | Medium | Array, Backtracking |
| 1774 | Closest Dessert Cost | Medium | Array, Dynamic Programming, Backtracking |
| 1849 | Splitting a String Into Descending Consecutive Values | Medium | String, Backtracking, Enumeration |
| 1947 | Maximum Compatibility Score Sum | Medium | Bit Manipulation, Array, Dynamic Programming +2 |
| 1980 | Find Unique Binary String | Medium | Array, Hash Table, String +1 |
| 1986 | Minimum Number of Work Sessions to Finish the Tasks | Medium | Bit Manipulation, Array, Dynamic Programming +2 |
| 2002 | Maximum Product of the Length of Two Palindromic Subsequences | Medium | Bit Manipulation, String, Dynamic Programming +2 |
| 2044 | Count Number of Maximum Bitwise-OR Subsets | Medium | Bit Manipulation, Array, Backtracking +1 |
| 2048 | Next Greater Numerically Balanced Number | Medium | Hash Table, Math, Backtracking +2 |
| 2178 | Maximum Split of Positive Even Integers | Medium | Greedy, Math, Backtracking |
| 2212 | Maximum Points in an Archery Competition | Medium | Bit Manipulation, Array, Backtracking +1 |
| 2305 | Fair Distribution of Cookies | Medium | Bit Manipulation, Array, Dynamic Programming +2 |
| 2375 | Construct Smallest Number From DI String | Medium | Stack, Greedy, String +1 |
| 2397 | Maximum Rows Covered by Columns | Medium | Bit Manipulation, Array, Backtracking +2 |
| 2597 | The Number of Beautiful Subsets | Medium | Array, Hash Table, Math +4 |
| 2698 | Find the Punishment Number of an Integer | Medium | Math, Backtracking |
| 2708 | Maximum Strength of a Group | Medium | Greedy, Bit Manipulation, Array +4 |
| 2767 | Partition String Into Minimum Beautiful Substrings | Medium | Hash Table, String, Dynamic Programming +1 |
| 254 | Factor CombinationsPremium | Medium | Backtracking |
| 267 | Palindrome Permutation IIPremium | Medium | Hash Table, String, Backtracking |
| 291 | Word Pattern IIPremium | Medium | Hash Table, String, Backtracking |
| 294 | Flip Game IIPremium | Medium | Memoization, Math, Dynamic Programming +2 |
| 320 | Generalized AbbreviationPremium | Medium | Bit Manipulation, String, Backtracking |
| 351 | Android Unlock PatternsPremium | Medium | Bit Manipulation, Dynamic Programming, Backtracking +1 |
| 681 | Next Closest TimePremium | Medium | Hash Table, String, Backtracking +1 |
| 1066 | Campus Bikes IIPremium | Medium | Bit Manipulation, Array, Dynamic Programming +2 |
| 1087 | Brace ExpansionPremium | Medium | Stack, Breadth-First Search, String +2 |
| 1215 | Stepping NumbersPremium | Medium | Breadth-First Search, Math, Backtracking |
| 1258 | Synonymous SentencesPremium | Medium | Sort, Union Find, Array +3 |
| 2152 | Minimum Number of Lines to Cover PointsPremium | Medium | Bit Manipulation, Geometry, Array +5 |
| 2664 | The Knight’s TourPremium | Medium | Array, Backtracking, Matrix |
| 2992 | Number of Self-Divisible PermutationsPremium | Medium | Bit Manipulation, Array, Math +4 |
Hard (31)
| # | Problem | Difficulty | Topics |
|---|---|---|---|
| 37 | Sudoku Solver | Hard | Array, Hash Table, Backtracking +1 |
| 51 | N-Queens | Hard | Array, Backtracking |
| 52 | N-Queens II | Hard | Backtracking |
| 126 | Word Ladder II | Hard | Breadth-First Search, Hash Table, String +1 |
| 140 | Word Break II | Hard | Trie, Memoization, Array +4 |
| 212 | Word Search II | Hard | Trie, Array, String +2 |
| 282 | Expression Add Operators | Hard | Math, String, Backtracking |
| 301 | Remove Invalid Parentheses | Hard | Breadth-First Search, String, Backtracking |
| 679 | 24 Game | Hard | Array, Math, Backtracking |
| 691 | Stickers to Spell Word | Hard | Bit Manipulation, Memoization, Array +5 |
| 773 | Sliding Puzzle | Hard | Breadth-First Search, Memoization, Array +3 |
| 980 | Unique Paths III | Hard | Bit Manipulation, Array, Backtracking +1 |
| 996 | Number of Squareful Arrays | Hard | Bit Manipulation, Array, Hash Table +4 |
| 1096 | Brace Expansion II | Hard | Stack, Breadth-First Search, Hash Table +3 |
| 1240 | Tiling a Rectangle with the Fewest Squares | Hard | Backtracking |
| 1255 | Maximum Score Words Formed by Letters | Hard | Bit Manipulation, Array, Hash Table +5 |
| 1307 | Verbal Arithmetic Puzzle | Hard | Array, Math, String +1 |
| 1467 | Probability of a Two Boxes Having The Same Number of Distinct Balls | Hard | Array, Math, Dynamic Programming +3 |
| 1601 | Maximum Number of Achievable Transfer Requests | Hard | Bit Manipulation, Array, Backtracking +1 |
| 1655 | Distribute Repeating Integers | Hard | Bit Manipulation, Array, Dynamic Programming +2 |
| 1723 | Find Minimum Time to Finish All Jobs | Hard | Bit Manipulation, Array, Dynamic Programming +2 |
| 1799 | Maximize Score After N Operations | Hard | Bit Manipulation, Array, Math +4 |
| 2014 | Longest Subsequence Repeated k Times | Hard | Greedy, String, Backtracking +2 |
| 2056 | Number of Valid Move Combinations On Chessboard | Hard | Array, String, Backtracking +1 |
| 2065 | Maximum Path Quality of a Graph | Hard | Graph, Array, Backtracking |
| 2151 | Maximum Good People Based on Statements | Hard | Bit Manipulation, Array, Backtracking +1 |
| 411 | Minimum Unique Word AbbreviationPremium | Hard | Bit Manipulation, Array, String +1 |
| 425 | Word SquaresPremium | Hard | Trie, Array, String +1 |
| 465 | Optimal Account BalancingPremium | Hard | Bit Manipulation, Array, Dynamic Programming +2 |
| 489 | Robot Room CleanerPremium | Hard | Backtracking, Interactive |
| 1088 | Confusing Number IIPremium | Hard | Math, Backtracking |
Keep exploring
All LeetCode topicsEvery tag with a page of its own, with the number of problems behind each.LeetCode patternsThe techniques themselves, with a Python template and complexity for each.Curated study listsBlind 75, NeetCode 150 and three more, grouped by pattern.Easy problemsStart here when the data structure is new rather than the problem.
Other topics
- Array1,569
- String672
- Hash Table588
- Math485
- Dynamic Programming481
- Sorting392
- Greedy346
- Depth-First Search289
- Binary Search253
- Database249
- Tree225
- Breadth-First Search223
- Matrix216
- Two Pointers201
- Bit Manipulation194
- Binary Tree174
- Heap (Priority Queue)163
- Prefix Sum157
- Stack157
- Simulation144
- Graph138
- Counting126
- Design122
- Sliding Window116
When the Backtracking problem arrives live
Stealth Interview is a desktop app for macOS and Windows. It reads the coding problem off your screen, returns a working solution with a step-by-step explanation and its time and space complexity, and transcribes what the interviewer is saying — while staying invisible to screen sharing.