Problem Forge
Choose sets so that every item is in exactly one chosen set.
{1, 2, 3}{4, 5, 6}{1, 4, 5}{2, 3, 6}{1, 2, 6}{3, 4, 5}
{1, 2, 3}{1, 4, 5}{2, 4, 6}{3, 5, 6}
This Month's Challenges: Exact Cover by 3-Sets (X3C)
This month's rungs
| rung | solved, all climbers | answers sent, all climbers | status |
|---|---|---|---|
| 2026-11-X3C-12 | 0 | 0 | unsolved |
| 2026-11-X3C-11 | 0 | 0 | unsolved |
| 2026-11-X3C-10 | 0 | 0 | unsolved |
| 2026-11-X3C-09 | 0 | 0 | unsolved |
| 2026-11-X3C-08 | 1 | 1 | solved |
| 2026-11-X3C-07 | 1 | 1 | solved |
| 2026-11-X3C-06 | 1 | 1 | solved |
| 2026-11-X3C-05 | 1 | 1 | solved |
| 2026-11-X3C-04 | 1 | 1 | solved |
| 2026-11-X3C-03 | 1 | 1 | solved |
| 2026-11-X3C-02 | 1 | 1 | solved |
| 2026-11-X3C-01 | 1 | 1 | solved |
| 2026-11-X3C-00 | 1 | 1 | solved |
Sign in to see your own progress and to open the rungs.
Samples
Five sample files, each with its answer. You need no account. To check your own answer, open a file on the Check page.
- SAMPLE-X3C-01.xc · 2724 items, 2160 sets · answer
- SAMPLE-X3C-02.xc · 2502 items, 1974 sets · answer
- SAMPLE-X3C-03.xc · 2526 items, 2007 sets · answer
- SAMPLE-X3C-04.xc · 3582 items, 2856 sets · answer
- SAMPLE-X3C-05.xc · 2550 items, 2022 sets · answer
Read more: references for Exact Cover by 3-Sets (X3C).