Topic 11 — Tree DFS
Finished Thu, Sep 3, 2026, 2:18 PM ET: all 3 core problems closed, 3 problems closed that day.
Scheduled: Thu Sep 3, 2026 · Phase: Phase III — Hierarchical · Topic: #13 · Builds on: recursion
Closed Sep 3 — the day the topic finished
| Issue | Problem | Set | Difficulty | Closed (ET) | Solution |
|---|---|---|---|---|---|
| #96 | LC 226 · Invert Binary Tree | core | easy | Sep 3 | py · docs |
| #97 | LC 104 · Maximum Depth of Binary Tree | core | easy | Sep 3 | py · docs |
| #98 | LC 236 · Lowest Common Ancestor | core | medium | Sep 3 | py · docs |
Open at release
| Issue | Problem | Set | Difficulty | Closed (ET) | Solution |
|---|---|---|---|---|---|
| #99 | LC 100 · Same Tree | optional | easy | — | — |
| #100 | LC 572 · Subtree of Another Tree | optional | easy | — | — |
| #101 | LC 101 · Symmetric Tree | optional | easy | — | — |
| #102 | LC 112 · Path Sum | optional | easy | — | — |
| #103 | LC 129 · Sum Root to Leaf Numbers | optional | medium | — | — |
| #104 | LC 543 · Diameter of Binary Tree | optional | easy | — | — |
| #105 | LC 124 · Binary Tree Maximum Path Sum | deferred | hard | — | — |
20260903.181810.000000000 is timever for the UTC instant the core set completed; it tags 9008251, the last main commit before it.