Topic 20 — Backtracking
Finished Thu, Sep 24, 2026, 2:36 PM ET: all 3 core problems closed, 3 problems closed that day.
Scheduled: Thu Sep 24, 2026 · Phase: Phase V — Decision Space · Topic: #22 · Builds on: Topic 16 — then unlocks LC 212 from Topic 15
Closed Sep 24 — the day the topic finished
| Issue | Problem | Set | Difficulty | Closed (ET) | Solution |
|---|---|---|---|---|---|
| #149 | LC 78 · Subsets | core | medium | Sep 24 | py · docs |
| #150 | LC 39 · Combination Sum | core | medium | Sep 24 | py · docs |
| #151 | LC 46 · Permutations | core | medium | Sep 24 | py · docs |
Open at release
| Issue | Problem | Set | Difficulty | Closed (ET) | Solution |
|---|---|---|---|---|---|
| #152 | LC 79 · Word Search | optional | medium | — | — |
| #153 | LC 22 · Generate Parentheses | optional | medium | — | — |
| #154 | LC 17 · Letter Combinations | optional | medium | — | — |
| #155 | LC 77 · Combinations | optional | medium | — | — |
| #156 | LC 52 · N-Queens II | deferred | hard | — | — |
| #218 | LC 90 · Subsets II | optional | medium | — | — |
| #221 | LC 131 · Palindrome Partitioning | optional | medium | — | — |
20260924.183638.000000000 is timever for the UTC instant the core set completed; it tags f0f479d, the last main commit before it.