| 17 | Letter Combinations of a Phone Number | Medium | backtracking |
| 22 | Generate Parentheses | Medium | backtracking |
| 37 | Sudoku Solver | Hard | backtracking |
| 39 | Combination Sum | Medium | backtracking |
| 40 | Combination Sum II | Medium | backtracking |
| 46 | Permutations | Medium | backtracking |
| 47 | Permutations II | Medium | backtracking |
| 51 | N-Queens | Hard | backtracking |
| 52 | N-Queens-II | Hard | backtracking |
| 77 | Combinations | Medium | backtracking |
| 78 | Subsets | Medium | backtracking |
| 79 | Word Search | Medium | backtracking |
| 90 | Subsets II | Medium | backtracking |
| 93 | Restore IP Addresses | Medium | backtracking |
| 112 | Path Sum | Easy | depth first search |
| 113 | Path Sum II | Medium | depth first search |
| 126 | Word Ladder II | Hard | backtracking |
| 131 | Palindrome Partitioning | Medium | backtracking |
| 140 | Word Break II | Hard | backtracking |
| 199 | Binary Tree Right Side View | Medium | depth first search |
| 200 | Number of Islands | Medium | depth first search |
| 211 | Add and Search Word - Data structure design | Medium | tree |
| 212 | Word Search II | Hard | backtracking |
| 216 | Combination Sum III | Medium | backtracking |
| 236 | Lowest Common Ancestor of a Binary Tree | Medium | depth first search |
| 247 | Strobogrammatic Number II | Medium | depth first search |
| 250 | Count Univalue Subtrees | Medium | depth first search |
| 254 | Factor Combinations | Medium | backtracking |
| 257 | Binary Tree Paths | Easy | depth first search |
| 267 | Palindrome Permutation II | Medium | backtracking |
| 269 | Alien Dictionary | Hard | breadth first search |
| 282 | Expression Add Operators | Hard | depth first search |
| 291 | Word Pattern II | Hard | backtracking |
| 297 | Serialize and Deserialize Binary Tree | Hard | tree |
| 301 | Remove Invalid Parentheses | Hard | depth first search |
| 307 | Range Sum Query - Mutable | Medium | tree |
| 308 | Range Sum Query 2D - Mutable | Hard | tree |
| 320 | Generalized Abbreviation | Medium | backtracking |
| 329 | Longest Increasing Path in a Matrix | Hard | depth first search |
| 339 | Nested List Weight Sum | Easy | depth first search |
| 351 | Android Unlock Patterns | Medium | dynamic programming |
| 357 | Count Numbers with Unique Digits | Medium | dynamic programming |
| 364 | Nested List Weight Sum II | Medium | depth first search |
| 366 | Find Leaves of Binary Tree | Medium | depth first search |
| 417 | Pacific Atlantic Water Flow | Medium | depth first search |
| 425 | Word Squares | Hard | backtracking |
| 440 | K-th Smallest in Lexicographical Order | Hard | depth first search |
| 464 | Can I Win | Medium | depth first search |
| 488 | Zuma Game | Hard | backtracking |
| 491 | Increasing Subsequences | Medium | backtracking |
| 508 | Most Frequent Subtree Sum | Medium | tree |
| 513 | Find Bottom Left Tree Value | Medium | tree |
| 515 | Find Largest Value in Each Tree Row | Medium | depth first search |
| 526 | Beautiful Arrangement | Medium | backtracking |
| 559 | Max Consecutive Ones | Easy | tree |
| 582 | Kill Process | Medium | depth first search |
| 638 | Shopping Offers | Medium | depth first search |
| 652 | Find Duplicate Subtrees | Medium | tree |
| 662 | Maximum Width of Binary Tree | Medium | tree |
| 676 | Implement Magic Dictionary | Medium | backtracking |
| 679 | 24 Game | Hard | backtracking |
| 690 | Employee Importance | Easy | depth first search |
| 691 | Stickers to Spell Word | Hard | dynamic programming |
| 694 | Number of Distinct Islands | Medium | depth first search |
| 695 | Max Area of Island | Easy | depth first search |
| 698 | Partition to K Equal Sum Subsets | Medium | backtracking |
| 711 | Number of Distinct Islands II | Hard | depth first search |
| 733 | Max Area of Island | Easy | depth first search |
| 749 | Contain Virus | Hard | depth first search |
| 753 | Cracking the Safe | Hard | depth first search |
| 756 | Pyramid Transition Matrix | Medium | depth first search |
| 784 | Letter Case Permutation | Easy | backtracking |
| 785 | Is Graph Bipartite? | Medium | depth first search |
| 797 | All Paths From Source to Target | Medium | depth first search |
| 802 | Find Eventual Safe States | Medium | depth first search |
| 814 | Binary Tree Pruning | Medium | tree |
| 827 | Making A Large Island | Hard | depth first search |
| 834 | Sum of Distances in Tree | Hard | depth first search |
| 841 | Keys and Rooms | Medium | depth first search |
| 851 | Loud and Rich | Medium | depth first search |
| 865 | Smallest Subtree with all the Deepest Nodes | Medium | tree |
| 889 | Construct Binary Tree from Preorder and Postorder Traversal | Medium | tree |
| 897 | Increasing Order Search Tree | Easy | tree |
| 934 | Shortest Bridge | Medium | breadth first search |
| 938 | Range Sum of BST | Medium | tree |
| 951 | Flip Equivalent Binary Trees | Medium | tree |
| 965 | Univalued Binary Tree | Easy | tree |
| 968 | Binary Tree Cameras | Hard | greedy |
| 971 | Flip Binary Tree To Match Preorder Traversal | Medium | tree |
| 979 | Distribute Coins in Binary Tree | Medium | tree |
| 987 | Vertical Order Traversal of a Binary Tree | Medium | tree |
| 988 | Smallest String Starting From Leaf | Medium | tree |
| 993 | Cousins in Binary Tree | Easy | tree |
| 996 | Number of Squareful Arrays | Hard | backtracking |
| 1020 | Number of Enclaves | Medium | depth first search |
| 1026 | Maximum Difference Between Node and Ancestor | Medium | tree |
| 1028 | Recover a Tree From Preorder Traversal | Hard | tree |
| 1038 | Binary Search Tree to Greater Sum Tree | Medium | tree |
| 1059 | All Paths from Source Lead to Destination | Medium | depth first search |
| 1079 | Letter Tile Possibilities | Medium | math |
| 1080 | Insufficient Nodes in Root to Leaf Paths | Medium | tree |
| 1087 | Brace Expansion | Medium | backtracking |
| 1096 | Brace Expansion II | Hard | backtracking |
| 1102 | Path With Maximum Minimum Value | Medium | breadth first search |
| 1120 | Maximum Average Subtree | Easy | tree |
| 1123 | Lowest Common Ancestor of Deepest Leaves | Medium | tree |
| 1145 | Binary Tree Coloring Game | Medium | tree |
| 1161 | Maximum Level Sum of a Binary Tree | Medium | breadth first search |
| 1192 | Critical Connections in a Network | Medium | depth first search |
| 1219 | Path with Maximum Gold | Medium | backtracking |
| 1240 | Tiling a Rectangle with the Fewest Squares | Hard | backtracking |
| 1254 | Number of Closed Islands | Medium | depth first search |
| 1255 | Maximum Score Words Formed by Letters | Hard | backtracking |
| 1261 | Find Elements in a Contaminated Binary Tree | Medium | tree |
| 1273 | Delete Tree Nodes | Medium | depth first search |
| 1307 | Verbal Arithmetic Puzzle | Hard | backtracking |
| 1315 | Sum of Nodes with Even-Valued Grandparent | Medium | depth first search |
| 1319 | Number of Operations to Make Network Connected | Medium | depth first search |
| 1325 | Delete Leaves With a Given Value | Medium | tree |
| 1339 | Maximum Product of Splitted Binary Tree | Medium | tree |
| 1361 | Validate Binary Tree Nodes | Medium | graph |
| 1372 | Longest ZigZag Path in a Binary Tree | Medium | depth first search |
| 1373 | Maximum Sum BST in Binary Tree | Hard | binary search tree |
| 1376 | Time Needed to Inform All Employees | Medium | depth first search |
| 1377 | Frog Position After T Seconds | Hard | depth first search |
| 1382 | Balance a Binary Search Tree | Medium | binary search tree |
| 1391 | Check if There is a Valid Path in a Grid | Medium | depth first search |
| 1430 | Check If a String Is a Valid Sequence from Root to Leaves Path in a Binary Tree | Medium | tree |
| 1443 | Minimum Time to Collect All Apples in a Tree | Medium | tree |
| 1448 | Count Good Nodes in Binary Tree | Medium | tree |
| 1457 | Pseudo-Palindromic Paths in a Binary Tree | Medium | tree |
| 1466 | Reorder Routes to Make All Paths Lead to the City Zero | Medium | depth first search |
| 1469 | Find All The Lonely Nodes | Easy | tree |
| 1485 | Clone Binary Tree With Random Pointer | Medium | depth first search |
| 1490 | Clone N-ary Tree | Medium | tree |
| 1516 | Move Sub-Tree of N-Ary Tree | Hard | tree |
| 1519 | Number of Nodes in the Sub-Tree With the Same Label | Medium | tree |
| 1522 | Diameter of N-Ary Tree | Medium | tree |
| 1530 | Number of Good Leaf Nodes Pairs | Medium | tree |
| 1568 | Minimum Number of Days to Disconnect Island | Medium | graph |
| 1593 | Split a String Into the Max Number of Unique Substrings | Medium | backtracking |
| 1601 | Maximum Number of Achievable Transfer Requests | Hard | graph |
| 1617 | Count Subtrees With Max Distance Between Cities | Hard | dynamic programming |
| 1631 | Path With Minimum Effort | Medium | graph |
| 1644 | Lowest Common Ancestor of a Binary Tree II | Medium | depth first search |
| 1659 | Maximize Grid Happiness | Hard | backtracking |
| 1676 | Lowest Common Ancestor of a Binary Tree IV | Medium | depth first search |
| 1681 | Minimum Incompatibility | Hard | dynamic programming |
| 1718 | Construct the Lexicographically Largest Valid Sequence | Medium | backtracking |
| 1723 | Find Minimum Time to Finish All Jobs | Hard | backtracking |
| 1740 | Find Distance in a Binary Tree | Medium | depth first search |
| 1766 | Tree of Coprimes | Hard | depth first search |
| 1778 | Shortest Path in a Hidden Grid | Medium | graph |
| 1810 | Minimum Path Cost in a Hidden Grid | Medium | graph |
| 1849 | Splitting a String Into Descending Consecutive Values | Medium | backtracking |
| 1858 | Longest Word With All Prefixes | Medium | string |
| 1905 | Count Sub Islands | Medium | depth first search |
| 1916 | Count Ways to Build Rooms in an Ant Colony | Hard | math |
| 1931 | Painting a Grid With Three Different Colors | Hard | dynamic programming |
| 1938 | Maximum Genetic Difference Query | Hard | tree |
| 1948 | Delete Duplicate Folders in System | Hard | tree |
| 1973 | Count Nodes Equal to Sum of Descendants | Medium | depth first search |
| 1999 | Smallest Greater Multiple Made of Two Digits | Medium | backtracking |
| 2003 | Smallest Missing Genetic Value in Each Subtree | Hard | tree |
| 2014 | Longest Subsequence Repeated k Times | Hard | backtracking |
| 2049 | Count Nodes With the Highest Score | Medium | depth first search |
| 2056 | Number of Valid Move Combinations On Chessboard | Hard | backtracking |
| 2065 | Maximum Path Quality of a Graph | Medium | depth first search |
| 2092 | Find All People With Secret | Hard | graph |
| 2094 | Finding 3-Digit Even Numbers | Easy | backtracking |
| 2096 | Step-By-Step Directions From a Binary Tree Node to Another | Medium | tree |
| 2184 | Number of Ways to Build Sturdy Brick Wall | Medium | dynamic programming |
| 2192 | All Ancestors of a Node in a Directed Acyclic Graph | Medium | depth first search |
| 2246 | Longest Path With Different Adjacent Characters | Hard | depth first search |
| 2265 | Count Nodes Equal to Average of Subtree | Medium | depth first search |
| 2307 | Check for Contradictions in Equations | Hard | graph |
| 2322 | Minimum Score After Removals on a Tree | Hard | depth first search |
| 2331 | Evaluate Boolean Binary Tree | Easy | depth first search |
| 2359 | Find Closest Node to Given Two Nodes | Medium | graph |
| 2360 | Longest Cycle in a Graph | Hard | graph |
| 2378 | Choose Edges to Maximize Score in a Tree | Medium | dynamic programming |
| 2385 | Amount of Time for Binary Tree to Be Infected | Medium | depth first search |
| 2440 | Create Components With Same Value | Hard | greedy |
| 2443 | Sum of Number and Its Reverse | Medium | backtracking |
| 2445 | Number of Nodes With Value One | Medium | depth first search |
| 2458 | Height of Binary Tree After Subtree Removal Queries | Hard | depth first search |
| 2467 | Most Profitable Path in a Tree | Medium | depth first search |
| 2476 | Closest Nodes Queries in a Binary Search Tree | Hard | binary search |
| 2477 | Minimum Fuel Cost to Report to the Capital | Medium | depth first search |
| 2479 | Maximum XOR of Two Non-Overlapping Subtrees | Hard | greedy |
| 2493 | Divide Nodes Into the Maximum Number of Groups | Medium | breadth first search |
| 2538 | Difference Between Maximum and Minimum Price Sum | Hard | dynamic programming |
| 2556 | Disconnect Path in a Binary Matrix by at Most One Flip | Medium | dynamic programming |
| 2581 | Count Number of Possible Root Nodes | Hard | depth first search |
| 2625 | Flatten Deeply Nested Array | Medium | design |
| 2628 | JSON Deep Equal | Medium | design |
| 2633 | Convert Object to JSON String | Medium | design |
| 2646 | Minimize the Total Price of the Trips | Hard | dynamic programming |
| 2649 | Nested Array Generator | Medium | design |
| 2658 | Maximum Number of Fish in a Grid | Medium | breadth first search |
| 2664 | The Knight’s Tour | Medium | backtracking |
| 2675 | Array of Objects to Matrix | Medium | design |
| 2698 | Find the Punishment Number of an Integer | Medium | backtracking |
| 2700 | Differences Between Two Objects | Medium | design |
| 2705 | Compact Object | Medium | design |
| 2741 | Special Permutations | Medium | backtracking |
| 2755 | Deep Merge of Two Objects | Medium | design |
| 2773 | Height of Special Binary Tree | Medium | depth first search |
| 2775 | Undefined to Null | Medium | design |
| 2791 | Count Paths That Can Form a Palindrome in a Tree | Hard | depth first search |
| 2823 | Deep Object Filter | Medium | design |
| 2850 | Minimum Moves to Spread Stones Over Grid | Medium | graph |
| 2858 | Minimum Edge Reversals So Every Node Is Reachable | Hard | dynamic programming |
| 2867 | Count Valid Paths in a Tree | Hard | dynamic programming |
| 2920 | Maximum Points After Collecting Coins From All Nodes | Hard | dynamic programming |
| 2925 | Maximum Score After Applying Operations on a Tree | Medium | dynamic programming |
| 2959 | Number of Possible Sets of Closing Branches | Medium | graph |
| 2973 | Find Number of Coins to Place in Tree Nodes | Hard | depth first search |
| 3004 | Maximum Subtree of the Same Color | Medium | depth first search |
| 3067 | Count Pairs of Connectable Servers in a Weighted Tree Network | Medium | depth first search |
| 3203 | Find Minimum Diameter After Merging Two Trees | Hard | depth first search |
| 3211 | Generate Binary Strings Without Adjacent Zeros | Medium | backtracking |
| 3235 | Check if the Rectangle Corner Is Reachable | Hard | graph |
| 3241 | Time Taken to Mark All Nodes | Hard | dynamic programming |
| 3249 | Count the Number of Good Nodes | Medium | depth first search |
| 3313 | Find the Last Marked Nodes in Tree | Hard | dynamic programming |
| 3319 | K-th Largest Perfect Subtree Size in Binary Tree | Medium | depth first search |
| 3327 | Check if DFS Strings Are Palindromes | Hard | depth first search |
| 3331 | Find Subtree Sizes After Changes | Medium | depth first search |
| 3367 | Maximize Sum of Weights after Edge Removals | Hard | depth first search |
| 3372 | Maximize the Number of Target Nodes After Connecting Trees I | Medium | dynamic programming |
| 3425 | Longest Special Path | Hard | two pointers |
| 3437 | Permutations III | Medium | backtracking |
| 3486 | Longest Special Path II | Hard | two pointers |
| 3515 | Shortest Path in a Weighted Tree | Hard | tree |
| 3544 | Subtree Inversion Sum | Hard | dynamic programming |
| 3553 | Minimum Weighted Subgraph With the Required Paths II | Hard | tree |
| 3559 | Number of Ways to Assign Edge Weights II | Medium | tree |
| 3562 | Maximum Profit from Trading Stocks with Discounts | Hard | dynamic programming |
| 3565 | Sequential Grid Path Cover | Medium | backtracking |
| 3575 | Maximum Good Subtree Score | Hard | dynamic programming |
| 3585 | Find Weighted Median Node in Tree | Hard | tree |
| 3590 | Kth Smallest Path XOR Sum | Hard | depth first search |
| 3593 | Minimum Increments to Equalize Leaf Paths | Medium | depth first search |
| 3607 | Power Grid Maintenance | Medium | depth first search |
| 3669 | Balanced K-Factor Decomposition | Medium | backtracking |
| 3715 | Sum of Perfect Square Ancestors | Hard | tree |
| 3786 | Total Sum of Interaction Cost in Tree Groups | Hard | breadth first search |
| 3841 | Palindromic Path Queries in a Tree | Hard | tree |
| 3879 | Maximum Distinct Path Sum in a Binary Tree | Medium | tree |
| 3910 | Count Connected Subgraphs with Even Node Sum | Hard | graph |
| 3949 | Subtree Inversion Sum II | Hard | dynamic programming |
| 3955 | Valid Binary Strings With Cost Limit | Medium | backtracking |
| 3965 | Finish Time of Tasks I | Medium | dynamic programming |
| 3967 | Finish Time of Tasks II | Hard | dynamic programming |
| 3973 | Distinct Gate Paths to LCA | Hard | tree |