GridMew1Check row 8
row 8 has only one remaining candidate: row 8, column 1. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 1. Place one cat, then exclude 5 other cells.Puzzle gm-8-0009
8 × 8 challenge
Take this puzzle one clear step at a time.
Try the puzzle yourself, then explore how the deductions build.
Puzzle board · starting state
Your starting point
This original 8×8 board has 8 connected regions and 2 fixed cats. The smallest region is H, with 1 cell. Start by ruling out every other cell in each fixed cat’s row, column and region, plus its immediate neighbors.
The verified route below uses 6 forced placements and 3 candidate-elimination steps after the givens. Region sizes: A: 4 · B: 18 · C: 4 · D: 9 · E: 6 · F: 6 · G: 16 · H: 1. These are observations about this board, not a guarantee that a smaller region always contains the next move.
Read each diagram in sequence. Cats and × marks in the before-state come from earlier deductions. Green outlines identify the current observation. Open the final answer only when you want the spoiler.
Step-by-step walkthrough
2Check row 5
row 5 has only one remaining candidate: row 5, column 8. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 2. Place one cat, then exclude 5 other cells.3Use a candidate lock
Every candidate in column 2 lies in region B (row 1, column 2; row 2, column 2; row 3, column 2; row 4, column 2). Its cat must use that shared section. Exclude row 1, column 4; row 2, column 4 from the rest of region B.
Before step 3. Exclude 2 cells; then scan for a new single.4Use a candidate lock
Every candidate in column 4 lies in region D (row 3, column 4; row 4, column 4). Its cat must use that shared section. Exclude row 3, column 6 from the rest of region D.
Before step 4. Exclude 1 cells; then scan for a new single.5Exclude common neighbors
The cat in column 6 must occupy one of row 1, column 6; row 2, column 6. Each of row 1, column 7; row 2, column 7 touches every candidate, so none can hold a cat.
Before step 5. Exclude 2 cells; then scan for a new single.6Check column 7
column 7 has only one remaining candidate: row 3, column 7. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 6. Place one cat, then exclude 3 other cells.7Check row 2
row 2 has only one remaining candidate: row 2, column 2. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 7. Place one cat, then exclude 2 other cells.8Check row 1
row 1 has only one remaining candidate: row 1, column 6. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 8. Place one cat, then exclude 0 other cells.9Check row 4
row 4 has only one remaining candidate: row 4, column 4. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 9. Place one cat, then exclude 0 other cells.Show solution · reveals all cat positions
The final cats satisfy every row, column and region quota, with no edge or corner contact.
Cat positions: r1c6, r2c2, r3c7, r4c4, r5c8, r6c3, r7c5, r8c1.