GridMew1Check region E
region E has only one remaining candidate: row 5, column 4. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 1. Place one cat, then exclude 7 other cells.Combine a reserved row with its shared neighbors
Original puzzle gm-8-0001
By GridMew · Published 15 October 2026 · Updated 16 October 2026
8 × 8 challenge
Read the starting position, follow the deductions, and check the move that is easy to misread.
Puzzle board · starting state
How to approach this board
Coordinates such as r2c3 mean row 2, column 3. Count rows from the top and columns from the left.
Region E is the singleton r5c4. After placing it and resolving column 1 at r6c1, inspect the top two rows together. The givens leave a useful reservation there rather than an immediate top-row cat.
8×8 · 3 fixed cats · 7 explained deductions. Region sizes: A: 8 · B: 7 · C: 9 · D: 10 · E: 1 · F: 4 · G: 20 · H: 5.
A deduction worth checking
Row 2 can use r2c5 or r2c6. Both touch r1c5 and r1c6, so those disappear and row 1 is forced at r1c8.
A move to double-check · r2c8
The earlier row-1 reservation gives A its cat. r2c8 is also in A, so it must be removed even before the exact top-row location is known.
Green marks the cell being discussed, not a cat to place. This is the position before step 3; compare the deduction below.
Read the starting board as text
Each line is one row, left to right. Matching letters belong to the same connected region.
C C A A A A A A C C C B B B A A C C C B B D D D C G G B B D D D F G G E G D D D F G G G G G G D F G G G G G H H F G G G G H H H
Fixed cats: row 3, column 2; row 7, column 3; row 8, column 7. One cat is required in each row, column and region.
Step-by-step walkthrough
2Check column 1
column 1 has only one remaining candidate: row 6, column 1. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 2. Place one cat, then exclude 1 other cells.3Use a candidate lock
Every candidate in row 1 lies in region A (row 1, column 5; row 1, column 6; row 1, column 8). Its cat must use that shared section. Exclude row 2, column 8 from the rest of region A.
Before step 3. Exclude 1 cells; then scan for a new single.4Exclude common neighbors
The cat in row 2 must occupy one of row 2, column 5; row 2, column 6. Each of row 1, column 5; row 1, column 6 touches every candidate, so none can hold a cat.
Before step 4. Exclude 2 cells; then scan for a new single.5Check row 1
row 1 has only one remaining candidate: row 1, column 8. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 5. Place one cat, then exclude 1 other cells.6Check row 4
row 4 has only one remaining candidate: row 4, column 6. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 6. Place one cat, then exclude 1 other cells.7Check row 2
row 2 has only one remaining candidate: row 2, column 5. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 7. 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: r1c8, r2c5, r3c2, r4c6, r5c4, r6c1, r7c3, r8c7.
Try another puzzle
Successive column reservations cross the upper half
gm-8-0009 · 8×8 · challenge
Practice shared-neighbor exclusions on another 8×8 board.
Read this walkthrough →A shared neighborhood settles the right edge
gm-6-0007 · 6×6 · challenge
Transfer shared-neighbor exclusions to a 6×6 grid; compare how the candidates change.
Read this walkthrough →Let a lower row reserve the right-hand region
gm-8-0002 · 8×8 · challenge
Compare this route with candidate locks, and check why that different rule is needed.
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