Tree LeetCode Problems: All 225, With Python Solutions
Every problem in this library that LeetCode tags Tree — 225 in total, 167 of them with a complete Python solution, a worked example and the time and space complexity of the approach.
- 225 problems
- 41 Easy
- 142 Medium
- 42 Hard
How Tree problems are solved
A tag names the subject, not the method. These pattern hubs cover the techniques that actually solve Tree problems — each one explains the approach, gives a Python template and states its complexity.
- Tree Traversal — Choose the order — preorder, inorder, postorder, level — and the problem solves itself.
Tree problems by difficulty
Showing the first 200 of 225 problems. Problems with a complete Python solution are listed first, then by ascending problem number.
Easy (40)
| # | Problem | Difficulty | Topics |
|---|---|---|---|
| 94 | Binary Tree Inorder Traversal | Easy | Stack, Tree, Depth-First Search +1 |
| 100 | Same Tree | Easy | Tree, Depth-First Search, Breadth-First Search +1 |
| 101 | Symmetric Tree | Easy | Tree, Depth-First Search, Breadth-First Search +1 |
| 104 | Maximum Depth of Binary Tree | Easy | Tree, Depth-First Search, Breadth-First Search +1 |
| 108 | Convert Sorted Array to Binary Search Tree | Easy | Tree, Binary Search Tree, Array +2 |
| 110 | Balanced Binary Tree | Easy | Tree, Depth-First Search, Binary Tree |
| 111 | Minimum Depth of Binary Tree | Easy | Tree, Depth-First Search, Breadth-First Search +1 |
| 112 | Path Sum | Easy | Tree, Depth-First Search, Breadth-First Search +1 |
| 144 | Binary Tree Preorder Traversal | Easy | Stack, Tree, Depth-First Search +1 |
| 145 | Binary Tree Postorder Traversal | Easy | Stack, Tree, Depth-First Search +1 |
| 222 | Count Complete Tree Nodes | Easy | Bit Manipulation, Tree, Binary Search +1 |
| 226 | Invert Binary Tree | Easy | Tree, Depth-First Search, Breadth-First Search +1 |
| 257 | Binary Tree Paths | Easy | Tree, Depth-First Search, String +2 |
| 404 | Sum of Left Leaves | Easy | Tree, Depth-First Search, Breadth-First Search +1 |
| 501 | Find Mode in Binary Search Tree | Easy | Tree, Depth-First Search, Binary Search Tree +1 |
| 530 | Minimum Absolute Difference in BST | Easy | Tree, Depth-First Search, Breadth-First Search +2 |
| 543 | Diameter of Binary Tree | Easy | Tree, Depth-First Search, Binary Tree |
| 559 | Maximum Depth of N-ary Tree | Easy | Tree, Depth-First Search, Breadth-First Search |
| 563 | Binary Tree Tilt | Easy | Tree, Depth-First Search, Binary Tree |
| 572 | Subtree of Another Tree | Easy | Tree, Depth-First Search, Binary Tree +2 |
| 589 | N-ary Tree Preorder Traversal | Easy | Stack, Tree, Depth-First Search |
| 590 | N-ary Tree Postorder Traversal | Easy | Stack, Tree, Depth-First Search |
| 617 | Merge Two Binary Trees | Easy | Tree, Depth-First Search, Breadth-First Search +1 |
| 637 | Average of Levels in Binary Tree | Easy | Tree, Depth-First Search, Breadth-First Search +1 |
| 653 | Two Sum IV - Input is a BST | Easy | Tree, Depth-First Search, Breadth-First Search +4 |
| 671 | Second Minimum Node In a Binary Tree | Easy | Tree, Depth-First Search, Binary Tree |
| 700 | Search in a Binary Search Tree | Easy | Tree, Binary Search Tree, Binary Tree |
| 703 | Kth Largest Element in a Stream | Easy | Tree, Design, Binary Search Tree +3 |
| 783 | Minimum Distance Between BST Nodes | Easy | Tree, Depth-First Search, Breadth-First Search +2 |
| 872 | Leaf-Similar Trees | Easy | Tree, Depth-First Search, Binary Tree |
| 897 | Increasing Order Search Tree | Easy | Stack, Tree, Depth-First Search +2 |
| 938 | Range Sum of BST | Easy | Tree, Depth-First Search, Binary Search Tree +1 |
| 965 | Univalued Binary Tree | Easy | Tree, Depth-First Search, Breadth-First Search +1 |
| 993 | Cousins in Binary Tree | Easy | Tree, Depth-First Search, Breadth-First Search +1 |
| 1022 | Sum of Root To Leaf Binary Numbers | Easy | Tree, Depth-First Search, Binary Tree |
| 1379 | Find a Corresponding Node of a Binary Tree in a Clone of That Tree | Easy | Tree, Depth-First Search, Breadth-First Search +1 |
| 2236 | Root Equals Sum of Children | Easy | Tree, Binary Tree |
| 2331 | Evaluate Boolean Binary Tree | Easy | Tree, Depth-First Search, Binary Tree |
| 270 | Closest Binary Search Tree ValuePremium | Easy | Tree, Depth-First Search, Binary Search Tree +2 |
| 1469 | Find All The Lonely NodesPremium | Easy | Tree, Depth-First Search, Breadth-First Search +1 |
Medium (125)
| # | Problem | Difficulty | Topics |
|---|---|---|---|
| 95 | Unique Binary Search Trees II | Medium | Tree, Binary Search Tree, Dynamic Programming +2 |
| 96 | Unique Binary Search Trees | Medium | Tree, Binary Search Tree, Math +2 |
| 98 | Validate Binary Search Tree | Medium | Tree, Depth-First Search, Binary Search Tree +1 |
| 99 | Recover Binary Search Tree | Medium | Tree, Depth-First Search, Binary Search Tree +1 |
| 102 | Binary Tree Level Order Traversal | Medium | Tree, Breadth-First Search, Binary Tree |
| 103 | Binary Tree Zigzag Level Order Traversal | Medium | Tree, Breadth-First Search, Binary Tree |
| 105 | Construct Binary Tree from Preorder and Inorder Traversal | Medium | Tree, Array, Hash Table +2 |
| 106 | Construct Binary Tree from Inorder and Postorder Traversal | Medium | Tree, Array, Hash Table +2 |
| 107 | Binary Tree Level Order Traversal II | Medium | Tree, Breadth-First Search, Binary Tree |
| 109 | Convert Sorted List to Binary Search Tree | Medium | Tree, Binary Search Tree, Linked List +2 |
| 113 | Path Sum II | Medium | Tree, Depth-First Search, Backtracking +1 |
| 114 | Flatten Binary Tree to Linked List | Medium | Stack, Tree, Depth-First Search +2 |
| 116 | Populating Next Right Pointers in Each Node | Medium | Tree, Depth-First Search, Breadth-First Search +2 |
| 117 | Populating Next Right Pointers in Each Node II | Medium | Tree, Depth-First Search, Breadth-First Search +2 |
| 129 | Sum Root to Leaf Numbers | Medium | Tree, Depth-First Search, Binary Tree |
| 173 | Binary Search Tree Iterator | Medium | Stack, Tree, Design +3 |
| 199 | Binary Tree Right Side View | Medium | Tree, Depth-First Search, Breadth-First Search +1 |
| 230 | Kth Smallest Element in a BST | Medium | Tree, Depth-First Search, Binary Search Tree +1 |
| 235 | Lowest Common Ancestor of a Binary Search Tree | Medium | Tree, Depth-First Search, Binary Search Tree +1 |
| 236 | Lowest Common Ancestor of a Binary Tree | Medium | Tree, Depth-First Search, Binary Tree |
| 331 | Verify Preorder Serialization of a Binary Tree | Medium | Stack, Tree, String +1 |
| 337 | House Robber III | Medium | Tree, Depth-First Search, Dynamic Programming +1 |
| 341 | Flatten Nested List Iterator | Medium | Stack, Tree, Depth-First Search +3 |
| 427 | Construct Quad Tree | Medium | Tree, Array, Divide and Conquer +1 |
| 429 | N-ary Tree Level Order Traversal | Medium | Tree, Breadth-First Search |
| 437 | Path Sum III | Medium | Tree, Depth-First Search, Binary Tree |
| 449 | Serialize and Deserialize BST | Medium | Tree, Depth-First Search, Breadth-First Search +4 |
| 450 | Delete Node in a BST | Medium | Tree, Binary Search Tree, Binary Tree |
| 508 | Most Frequent Subtree Sum | Medium | Tree, Depth-First Search, Hash Table +1 |
| 513 | Find Bottom Left Tree Value | Medium | Tree, Depth-First Search, Breadth-First Search +1 |
| 515 | Find Largest Value in Each Tree Row | Medium | Tree, Depth-First Search, Breadth-First Search +1 |
| 538 | Convert BST to Greater Tree | Medium | Tree, Depth-First Search, Binary Search Tree +1 |
| 558 | Logical OR of Two Binary Grids Represented as Quad-Trees | Medium | Tree, Divide and Conquer |
| 606 | Construct String from Binary Tree | Medium | Tree, Depth-First Search, String +1 |
| 623 | Add One Row to Tree | Medium | Tree, Depth-First Search, Breadth-First Search +1 |
| 652 | Find Duplicate Subtrees | Medium | Tree, Depth-First Search, Hash Table +1 |
| 654 | Maximum Binary Tree | Medium | Stack, Tree, Array +3 |
| 655 | Print Binary Tree | Medium | Tree, Depth-First Search, Breadth-First Search +1 |
| 662 | Maximum Width of Binary Tree | Medium | Tree, Depth-First Search, Breadth-First Search +1 |
| 669 | Trim a Binary Search Tree | Medium | Tree, Depth-First Search, Binary Search Tree +1 |
| 687 | Longest Univalue Path | Medium | Tree, Depth-First Search, Binary Tree |
| 690 | Employee Importance | Medium | Tree, Depth-First Search, Breadth-First Search +2 |
| 701 | Insert into a Binary Search Tree | Medium | Tree, Binary Search Tree, Binary Tree |
| 814 | Binary Tree Pruning | Medium | Tree, Depth-First Search, Binary Tree |
| 863 | All Nodes Distance K in Binary Tree | Medium | Tree, Depth-First Search, Breadth-First Search +2 |
| 865 | Smallest Subtree with all the Deepest Nodes | Medium | Tree, Depth-First Search, Breadth-First Search +2 |
| 889 | Construct Binary Tree from Preorder and Postorder Traversal | Medium | Tree, Array, Hash Table +2 |
| 894 | All Possible Full Binary Trees | Medium | Tree, Recursion, Memoization +2 |
| 919 | Complete Binary Tree Inserter | Medium | Tree, Breadth-First Search, Design +1 |
| 951 | Flip Equivalent Binary Trees | Medium | Tree, Depth-First Search, Binary Tree |
| 958 | Check Completeness of a Binary Tree | Medium | Tree, Breadth-First Search, Binary Tree |
| 971 | Flip Binary Tree To Match Preorder Traversal | Medium | Tree, Depth-First Search, Binary Tree |
| 979 | Distribute Coins in Binary Tree | Medium | Tree, Depth-First Search, Binary Tree |
| 988 | Smallest String Starting From Leaf | Medium | Tree, Depth-First Search, String +2 |
| 998 | Maximum Binary Tree II | Medium | Tree, Binary Tree |
| 1008 | Construct Binary Search Tree from Preorder Traversal | Medium | Stack, Tree, Binary Search Tree +3 |
| 1026 | Maximum Difference Between Node and Ancestor | Medium | Tree, Depth-First Search, Binary Tree |
| 1038 | Binary Search Tree to Greater Sum Tree | Medium | Tree, Depth-First Search, Binary Search Tree +1 |
| 1080 | Insufficient Nodes in Root to Leaf Paths | Medium | Tree, Depth-First Search, Binary Tree |
| 1104 | Path In Zigzag Labelled Binary Tree | Medium | Tree, Math, Binary Tree |
| 1110 | Delete Nodes And Return Forest | Medium | Tree, Depth-First Search, Array +2 |
| 1123 | Lowest Common Ancestor of Deepest Leaves | Medium | Tree, Depth-First Search, Breadth-First Search +2 |
| 1145 | Binary Tree Coloring Game | Medium | Tree, Depth-First Search, Binary Tree |
| 1161 | Maximum Level Sum of a Binary Tree | Medium | Tree, Depth-First Search, Breadth-First Search +1 |
| 1261 | Find Elements in a Contaminated Binary Tree | Medium | Tree, Depth-First Search, Breadth-First Search +3 |
| 1302 | Deepest Leaves Sum | Medium | Tree, Depth-First Search, Breadth-First Search +1 |
| 1305 | All Elements in Two Binary Search Trees | Medium | Tree, Depth-First Search, Binary Search Tree +2 |
| 1315 | Sum of Nodes with Even-Valued Grandparent | Medium | Tree, Depth-First Search, Breadth-First Search +1 |
| 1325 | Delete Leaves With a Given Value | Medium | Tree, Depth-First Search, Binary Tree |
| 1339 | Maximum Product of Splitted Binary Tree | Medium | Tree, Depth-First Search, Binary Tree |
| 1361 | Validate Binary Tree Nodes | Medium | Tree, Depth-First Search, Breadth-First Search +3 |
| 1367 | Linked List in Binary Tree | Medium | Tree, Depth-First Search, Linked List +1 |
| 1372 | Longest ZigZag Path in a Binary Tree | Medium | Tree, Depth-First Search, Dynamic Programming +1 |
| 1376 | Time Needed to Inform All Employees | Medium | Tree, Depth-First Search, Breadth-First Search |
| 1382 | Balance a Binary Search Tree | Medium | Greedy, Tree, Depth-First Search +3 |
| 1443 | Minimum Time to Collect All Apples in a Tree | Medium | Tree, Depth-First Search, Breadth-First Search +1 |
| 1448 | Count Good Nodes in Binary Tree | Medium | Tree, Depth-First Search, Breadth-First Search +1 |
| 1457 | Pseudo-Palindromic Paths in a Binary Tree | Medium | Bit Manipulation, Tree, Depth-First Search +2 |
| 1519 | Number of Nodes in the Sub-Tree With the Same Label | Medium | Tree, Depth-First Search, Breadth-First Search +2 |
| 1530 | Number of Good Leaf Nodes Pairs | Medium | Tree, Depth-First Search, Binary Tree |
| 1600 | Throne Inheritance | Medium | Tree, Depth-First Search, Design +1 |
| 1609 | Even Odd Tree | Medium | Tree, Breadth-First Search, Binary Tree |
| 1993 | Operations on Tree | Medium | Tree, Depth-First Search, Breadth-First Search +3 |
| 2049 | Count Nodes With the Highest Score | Medium | Tree, Depth-First Search, Array +1 |
| 2096 | Step-By-Step Directions From a Binary Tree Node to Another | Medium | Tree, Depth-First Search, String +1 |
| 2196 | Create Binary Tree From Descriptions | Medium | Tree, Array, Hash Table +1 |
| 2265 | Count Nodes Equal to Average of Subtree | Medium | Tree, Depth-First Search, Binary Tree |
| 2368 | Reachable Nodes With Restrictions | Medium | Tree, Depth-First Search, Breadth-First Search +4 |
| 2385 | Amount of Time for Binary Tree to Be Infected | Medium | Tree, Depth-First Search, Breadth-First Search +2 |
| 2415 | Reverse Odd Levels of Binary Tree | Medium | Tree, Depth-First Search, Breadth-First Search +1 |
| 2467 | Most Profitable Path in a Tree | Medium | Tree, Depth-First Search, Breadth-First Search +2 |
| 2471 | Minimum Number of Operations to Sort a Binary Tree by Level | Medium | Tree, Breadth-First Search, Binary Tree |
| 2476 | Closest Nodes Queries in a Binary Search Tree | Medium | Tree, Depth-First Search, Binary Search Tree +3 |
| 2477 | Minimum Fuel Cost to Report to the Capital | Medium | Tree, Depth-First Search, Breadth-First Search +1 |
| 2583 | Kth Largest Sum in a Binary Tree | Medium | Tree, Breadth-First Search, Binary Tree +1 |
| 2641 | Cousins in Binary Tree II | Medium | Tree, Depth-First Search, Breadth-First Search +2 |
| 2673 | Make Costs of Paths Equal in a Binary Tree | Medium | Greedy, Tree, Array +2 |
| 2925 | Maximum Score After Applying Operations on a Tree | Medium | Tree, Depth-First Search, Dynamic Programming |
| 156 | Binary Tree Upside DownPremium | Medium | Tree, Depth-First Search, Binary Tree |
| 250 | Count Univalue SubtreesPremium | Medium | Tree, Depth-First Search, Binary Tree |
| 255 | Verify Preorder Sequence in Binary Search TreePremium | Medium | Stack, Tree, Binary Search Tree +4 |
| 285 | Inorder Successor in BSTPremium | Medium | Tree, Depth-First Search, Binary Search Tree +1 |
| 298 | Binary Tree Longest Consecutive SequencePremium | Medium | Tree, Depth-First Search, Binary Tree |
| 314 | Binary Tree Vertical Order TraversalPremium | Medium | Tree, Depth-First Search, Breadth-First Search +3 |
| 333 | Largest BST SubtreePremium | Medium | Tree, Depth-First Search, Binary Search Tree +2 |
| 366 | Find Leaves of Binary TreePremium | Medium | Tree, Depth-First Search, Binary Tree |
| 426 | Convert Binary Search Tree to Sorted Doubly Linked ListPremium | Medium | Stack, Tree, Depth-First Search +4 |
| 510 | Inorder Successor in BST IIPremium | Medium | Tree, Binary Search Tree, Binary Tree |
| 536 | Construct Binary Tree from StringPremium | Medium | Stack, Tree, Depth-First Search +2 |
| 545 | Boundary of Binary TreePremium | Medium | Tree, Depth-First Search, Binary Tree |
| 549 | Binary Tree Longest Consecutive Sequence IIPremium | Medium | Tree, Depth-First Search, Binary Tree |
| 582 | Kill ProcessPremium | Medium | Tree, Depth-First Search, Breadth-First Search +2 |
| 663 | Equal Tree PartitionPremium | Medium | Tree, Depth-First Search, Binary Tree |
| 666 | Path Sum IVPremium | Medium | Tree, Depth-First Search, Array +2 |
| 742 | Closest Leaf in a Binary TreePremium | Medium | Tree, Depth-First Search, Breadth-First Search +1 |
| 776 | Split BSTPremium | Medium | Tree, Binary Search Tree, Recursion +1 |
| 1120 | Maximum Average SubtreePremium | Medium | Tree, Depth-First Search, Binary Tree |
| 1214 | Two Sum BSTsPremium | Medium | Stack, Tree, Depth-First Search +4 |
| 1245 | Tree DiameterPremium | Medium | Tree, Depth-First Search, Breadth-First Search +2 |
| 1257 | Smallest Common RegionPremium | Medium | Tree, Depth-First Search, Breadth-First Search +3 |
| 1273 | Delete Tree NodesPremium | Medium | Tree, Depth-First Search, Breadth-First Search +1 |
| 1430 | Check If a String Is a Valid Sequence from Root to Leaves Path in a Binary TreePremium | Medium | Tree, Depth-First Search, Breadth-First Search +1 |
| 1485 | Clone Binary Tree With Random PointerPremium | Medium | Tree, Depth-First Search, Breadth-First Search +2 |
| 1490 | Clone N-ary TreePremium | Medium | Tree, Depth-First Search, Breadth-First Search +1 |
| 1506 | Find Root of N-Ary TreePremium | Medium | Bit Manipulation, Tree, Depth-First Search +1 |
Hard (35)
| # | Problem | Difficulty | Topics |
|---|---|---|---|
| 124 | Binary Tree Maximum Path Sum | Hard | Tree, Depth-First Search, Dynamic Programming +1 |
| 297 | Serialize and Deserialize Binary Tree | Hard | Tree, Depth-First Search, Breadth-First Search +3 |
| 834 | Sum of Distances in Tree | Hard | Tree, Depth-First Search, Graph +1 |
| 968 | Binary Tree Cameras | Hard | Tree, Depth-First Search, Dynamic Programming +1 |
| 987 | Vertical Order Traversal of a Binary Tree | Hard | Tree, Depth-First Search, Breadth-First Search +3 |
| 1028 | Recover a Tree From Preorder Traversal | Hard | Tree, Depth-First Search, String +1 |
| 1373 | Maximum Sum BST in Binary Tree | Hard | Tree, Depth-First Search, Binary Search Tree +2 |
| 1377 | Frog Position After T Seconds | Hard | Tree, Depth-First Search, Breadth-First Search +1 |
| 1483 | Kth Ancestor of a Tree Node | Hard | Bit Manipulation, Tree, Depth-First Search +4 |
| 1569 | Number of Ways to Reorder Array to Get Same BST | Hard | Tree, Union Find, Binary Search Tree +7 |
| 1617 | Count Subtrees With Max Distance Between Cities | Hard | Bit Manipulation, Tree, Dynamic Programming +2 |
| 1719 | Number Of Ways To Reconstruct A Tree | Hard | Tree, Graph |
| 1766 | Tree of Coprimes | Hard | Tree, Depth-First Search, Array +2 |
| 1916 | Count Ways to Build Rooms in an Ant Colony | Hard | Tree, Graph, Topological Sort +3 |
| 2003 | Smallest Missing Genetic Value in Each Subtree | Hard | Tree, Depth-First Search, Union Find +1 |
| 2246 | Longest Path With Different Adjacent Characters | Hard | Tree, Depth-First Search, Graph +3 |
| 2322 | Minimum Score After Removals on a Tree | Hard | Bit Manipulation, Tree, Depth-First Search +1 |
| 2421 | Number of Good Paths | Hard | Tree, Union Find, Graph +3 |
| 2440 | Create Components With Same Value | Hard | Tree, Depth-First Search, Array +2 |
| 2458 | Height of Binary Tree After Subtree Removal Queries | Hard | Tree, Depth-First Search, Breadth-First Search +2 |
| 2509 | Cycle Length Queries in a Tree | Hard | Tree, Array, Binary Tree |
| 2538 | Difference Between Maximum and Minimum Price Sum | Hard | Tree, Depth-First Search, Array +1 |
| 2581 | Count Number of Possible Root Nodes | Hard | Tree, Depth-First Search, Array +2 |
| 2603 | Collect Coins in a Tree | Hard | Tree, Graph, Topological Sort +1 |
| 2646 | Minimize the Total Price of the Trips | Hard | Tree, Depth-First Search, Graph +2 |
| 2791 | Count Paths That Can Form a Palindrome in a Tree | Hard | Bit Manipulation, Tree, Depth-First Search +2 |
| 2846 | Minimum Edge Weight Equilibrium Queries in a Tree | Hard | Tree, Graph, Array +1 |
| 2867 | Count Valid Paths in a Tree | Hard | Tree, Depth-First Search, Math +2 |
| 2872 | Maximum Number of K-Divisible Components | Hard | Tree, Depth-First Search |
| 2920 | Maximum Points After Collecting Coins From All Nodes | Hard | Bit Manipulation, Tree, Depth-First Search +3 |
| 2973 | Find Number of Coins to Place in Tree Nodes | Hard | Tree, Depth-First Search, Dynamic Programming +2 |
| 272 | Closest Binary Search Tree Value IIPremium | Hard | Stack, Tree, Depth-First Search +4 |
| 428 | Serialize and Deserialize N-ary TreePremium | Hard | Tree, Depth-First Search, Breadth-First Search +1 |
| 431 | Encode N-ary Tree to Binary TreePremium | Hard | Tree, Depth-First Search, Breadth-First Search +2 |
| 1516 | Move Sub-Tree of N-Ary TreePremium | Hard | Tree, Depth-First Search |
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
- Breadth-First Search223
- Matrix216
- Two Pointers201
- Bit Manipulation194
- Binary Tree174
- Heap (Priority Queue)163
- Prefix Sum157
- Stack157
- Simulation144
- Graph138
- Counting126
- Design122
- Sliding Window116
- Backtracking105
When the Tree 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.