GridMew1Exclude common neighbors
The cat in row 3 must occupy one of row 3, column 1; row 3, column 2; row 3, column 3. Each of row 2, column 2 touches every candidate, so none can hold a cat.
Before step 1. Exclude 1 cells; then scan for a new single.A column reservation unlocks a small top region
Original puzzle gm-5-0012
By GridMew · Published 15 October 2026 · Updated 16 October 2026
5 × 5 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.
The right-edge given leaves several open-looking groups. Start with row 3’s common neighbors, then use column reservations. The two-cell region A becomes forced only after those eliminations.
5×5 · 1 fixed cats · 8 explained deductions. Region sizes: A: 2 · B: 6 · C: 7 · D: 6 · E: 4.
A deduction worth checking
Column 4’s candidates r1c4 and r2c4 both lie in B. B cannot use r2c3 outside that column; the following neighbor step then removes r1c3.
A move to double-check · r2c3
The column lock removes r2c3 without deciding whether column 4’s cat is above or below it. Keeping both column candidates is essential to the argument.
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 A A B B C B B B D C C E B D C C E D D C E E D D
Fixed cats: row 4, column 5. One cat is required in each row, column and region.
Step-by-step walkthrough
2Use a candidate lock
Every candidate in column 1 lies in region C (row 1, column 1; row 2, column 1; row 3, column 1; row 5, column 1). Its cat must use that shared section. Exclude row 3, column 2 from the rest of region C.
Before step 2. Exclude 1 cells; then scan for a new single.3Use a candidate lock
Every candidate in column 4 lies in region B (row 1, column 4; row 2, column 4). Its cat must use that shared section. Exclude row 2, column 3 from the rest of region B.
Before step 3. Exclude 1 cells; then scan for a new single.4Exclude common neighbors
The cat in column 4 must occupy one of row 1, column 4; row 2, column 4. Each of row 1, column 3 touches every candidate, so none can hold a cat.
Before step 4. Exclude 1 cells; then scan for a new single.5Check region A
region A has only one remaining candidate: row 1, column 2. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 5. Place one cat, then exclude 4 other cells.6Check row 2
row 2 has only one remaining candidate: row 2, column 4. 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 3
row 3 has only one remaining candidate: row 3, column 1. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 7. Place one cat, then exclude 1 other cells.8Check row 5
row 5 has only one remaining candidate: row 5, column 3. 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.Show solution · reveals all cat positions
The final cats satisfy every row, column and region quota, with no edge or corner contact.
Cat positions: r1c2, r2c4, r3c1, r4c5, r5c3.
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