Claude Opus 5.5 on Beyond grid 4
Solved: 57 of 57 blank cells right. It said it was 99% sure. All of Claude Opus 5.5's answers.
RESULTSolved
CELLS RIGHT57 / 57
SAID99% sure
MODEL TIME2.0 min
COST$0.289 (API-equivalent)
TOKENS IN / OUT911 / 14,079
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5 given 5 filled correctly 53 wrong, with the right digit 3 left empty
The end of its reply
The grid passes a full check: every row, column and box contains 1–9 exactly once, and all 24 givens are unchanged.
**How it was solved**
1. **Forced placements.** Single-candidate and single-position checks gave r1c1=4, r1c3=7, r8c4=7, r3c6=7, r7c4=3, r9c3=2, r5c2=2, r7c2=8, r8c2=3, r8c3=5, r6c1=8, r4c1=7, r4c3=3 and r4c8=1.
2. **Branch point in box 9.** Row 8 still needed 1, 4, 8 and 9. The 4 had to go in r8c8 or r8c9. That left two cases: either {r8c8, r8c9} = {4,8}, or {r8c8, r8c9} = {4,9}.
3. **The {4,8} case.** I followed this case through and it fills every cell without contradiction:
- Box 8 and column 1 resolve, which fixes column 6 and box 5.
- Then column 4 and column 9 resolve (r2c9=5, r4c9=6, r3c9=9, r6c9=2, r1c9=3).
- Rows 1 and 3 follow, then column 7 (r7c7=9), and the rest falls into place.
4. **The other case.** I did not test the {4,9} case to a contradiction. Since the puzzle has exactly one solution and the first case produces a valid complete grid, that grid must be the answer.
<grid>
497158623
261943875
358267149
743892516
529671438
816534792
184325967
935716284
672489351
</grid>
<confidence>99</confidence>Grid beyond-3 of set v1, 24 givens. Puzzle as one line: .....8...261..3...3.8...1...4.89....5...7..3..1..3......4.2...7.....62...7.4....1