GridMew1Check region A
region A has only one remaining candidate: row 1, column 1. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 1. Place one cat, then exclude 9 other cells.A forced corner is only the beginning
Original puzzle gm-5-0014
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.
Region A is a single top-left cell, but placing it does not finish the reasoning. Follow the remaining neighborhoods in row 2 and column 2 before using the right-edge region’s lock.
5×5 · 0 fixed cats · 9 explained deductions. Region sizes: A: 1 · B: 5 · C: 9 · D: 2 · E: 8.
A deduction worth checking
Region D is confined to r4c5 and r5c5. It reserves column 5, so the higher candidates r2c5 and r3c5 disappear without choosing D’s row.
A move to double-check · r3c3
At step 4, every remaining candidate in C touches r3c3. This uses the candidates after earlier exclusions, not all cells that originally carried the letter C.
Green marks the cell being discussed, not a cat to place. This is the position before step 4; 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.
A C C B B C C C B B C C E E B C C E E D E E E E D
Fixed cats: none. One cat is required in each row, column and region.
Step-by-step walkthrough
2Exclude common neighbors
The cat in row 2 must occupy one of row 2, column 3; row 2, column 4; row 2, column 5. Each of row 3, column 4 touches every candidate, so none can hold a cat.
Before step 2. Exclude 1 cells; then scan for a new single.3Exclude common neighbors
The cat in column 2 must occupy one of row 3, column 2; row 4, column 2; row 5, column 2. Each of row 4, column 3 touches every candidate, so none can hold a cat.
Before step 3. Exclude 1 cells; then scan for a new single.4Exclude common neighbors
The cat in region C must occupy one of row 2, column 3; row 3, column 2; row 4, column 2. Each of row 3, column 3 touches every candidate, so none can hold a cat.
Before step 4. Exclude 1 cells; then scan for a new single.5Use a candidate lock
Every candidate in region D lies in column 5 (row 4, column 5; row 5, column 5). Its cat must use that shared section. Exclude row 2, column 5; row 3, column 5 from the rest of column 5.
Before step 5. Exclude 2 cells; then scan for a new single.6Check row 3
row 3 has only one remaining candidate: row 3, column 2. 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 4. 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 4
row 4 has only one remaining candidate: row 4, column 5. Every other cell is excluded by earlier placements or deductions. Place the cat here.
Before step 8. Place one cat, then exclude 1 other cells.9Check 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 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: r1c1, r2c4, r3c2, r4c5, r5c3.
Try another puzzle
A column reservation unlocks a small top region
gm-5-0012 · 5×5 · challenge
Practice candidate locks on another 5×5 board.
Read this walkthrough →Two singleton regions set up a vertical lock
gm-6-0003 · 6×6 · challenge
Transfer candidate locks to a 6×6 grid; compare how the candidates change.
Read this walkthrough →Use column locks before placing the first cat
gm-5-0005 · 5×5 · challenge
Compare this route with single-candidate placements, and check why that different rule is needed.
Read this walkthrough →