Cats & Dogs #156: 8x8 Grid Puzzle (Medium)

medium

Tap a square: 🐱 cat → 🐶 dog → clear

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🐱 4 cats and 🐶 4 dogs in every row and column = same   × different

Use pure logic to place every cat and dog. Each row and column holds 4 of each animal, three in a row is never allowed, and the clues between squares settle the rest.

  • Exactly 4 cats and 4 dogs in every row and every column.
  • Never three of the same animal in a row, across or down.
  • An = between two squares means the same animal; a × means different animals.

Step-by-step solution

Squares are written as R<row>C<column>, counting from the top-left.

  1. The × clue between R1C1 and R1C2 means they are different. R1C1 is a cat, so R1C2 is a dog.
  2. The × clue between R2C5 and R2C4 means they are different. R2C5 is a dog, so R2C4 is a cat.
  3. The = clue between R5C6 and R5C5 means they are the same. R5C6 is a dog, so R5C5 is a dog.
  4. The × clue between R8C1 and R7C1 means they are different. R8C1 is a dog, so R7C1 is a cat.
  5. The = clue between R7C4 and R8C4 means they are the same. R7C4 is a dog, so R8C4 is a dog.
  6. The = clue between R8C4 and R8C5 means they are the same. R8C4 is a dog, so R8C5 is a dog.
  7. R2C3 and R2C4 are both cats, so R2C2 must be a dog (no three in a row).
  8. R2C5 and R2C7 are both dogs with one square between them, so R2C6 must be a cat.
  9. R5C5 and R5C6 are both dogs, so R5C4 must be a cat (no three in a row).
  10. R5C5 and R5C6 are both dogs, so R5C7 must be a cat (no three in a row).
  11. R8C4 and R8C5 are both dogs, so R8C3 must be a cat (no three in a row).
  12. R8C4 and R8C5 are both dogs, so R8C6 must be a cat (no three in a row).
  13. R1C2 and R2C2 are both dogs, so R3C2 must be a cat (no three in a row).
  14. R7C4 and R8C4 are both dogs, so R6C4 must be a cat (no three in a row).
  15. R6C4 and R6C5 are both cats, so R6C3 must be a dog (no three in a row).
  16. The = clue between R6C3 and R5C3 means they are the same. R6C3 is a dog, so R5C3 is a dog.
  17. R6C4 and R6C5 are both cats, so R6C6 must be a dog (no three in a row).
  18. R5C3 and R6C3 are both dogs, so R4C3 must be a cat (no three in a row).
  19. R2C3 and R4C3 are both cats with one square between them, so R3C3 must be a dog.
  20. R5C3 and R6C3 are both dogs, so R7C3 must be a cat (no three in a row).
  21. R7C1 and R7C3 are both cats with one square between them, so R7C2 must be a dog.
  22. R5C4 and R6C4 are both cats, so R4C4 must be a dog (no three in a row).
  23. R5C6 and R6C6 are both dogs, so R4C6 must be a cat (no three in a row).
  24. R2C6 and R4C6 are both cats with one square between them, so R3C6 must be a dog.
  25. R5C6 and R6C6 are both dogs, so R7C6 must be a cat (no three in a row).
  26. Row 5 already has its 4 dogs, so R5C1 must be cats.
  27. R5C1 and R7C1 are both cats with one square between them, so R6C1 must be a dog.
  28. R6C1 and R6C3 are both dogs with one square between them, so R6C2 must be a cat.
  29. Row 5 already has its 4 dogs, so R5C2 must be cats.
  30. R3C2 and R5C2 are both cats with one square between them, so R4C2 must be a dog.
  31. Row 6 already has its 4 cats, so R6C7 must be dogs.
  32. The × clue between R6C7 and R7C7 means they are different. R6C7 is a dog, so R7C7 is a cat.
  33. R7C6 and R7C7 are both cats, so R7C5 must be a dog (no three in a row).
  34. R7C6 and R7C7 are both cats, so R7C8 must be a dog (no three in a row).
  35. Column 2 already has its 4 dogs, so R8C2 must be cats.
  36. Column 3 already has its 4 cats, so R1C3 must be dogs.
  37. R1C2 and R1C3 are both dogs, so R1C4 must be a cat (no three in a row).
  38. R1C4 and R2C4 are both cats, so R3C4 must be a dog (no three in a row).
  39. R3C3 and R3C4 are both dogs, so R3C5 must be a cat (no three in a row).
  40. Column 5 already has its 4 dogs, so R1C5 must be cats.
  41. R1C4 and R1C5 are both cats, so R1C6 must be a dog (no three in a row).
  42. Column 5 already has its 4 dogs, so R4C5 must be cats.
  43. R4C5 and R4C6 are both cats, so R4C7 must be a dog (no three in a row).
  44. R2C7 and R4C7 are both dogs with one square between them, so R3C7 must be a cat.
  45. The × clue between R3C7 and R3C8 means they are different. R3C7 is a cat, so R3C8 is a dog.
  46. R3C8 and R5C8 are both dogs with one square between them, so R4C8 must be a cat.
  47. Row 3 already has its 4 dogs, so R3C1 must be cats.
  48. R1C1 and R3C1 are both cats with one square between them, so R2C1 must be a dog.
  49. R3C1 and R5C1 are both cats with one square between them, so R4C1 must be a dog.
  50. Row 2 already has its 4 dogs, so R2C8 must be cats.
  51. The = clue between R2C8 and R1C8 means they are the same. R2C8 is a cat, so R1C8 is a cat.
  52. Row 1 already has its 4 cats, so R1C7 must be dogs.
  53. Column 7 already has its 4 dogs, so R8C7 must be cats.
  54. R8C6 and R8C7 are both cats, so R8C8 must be a dog (no three in a row).

About this puzzle

This 8×8 grid starts with 10 filled squares and 10 = / × clues. It can be solved in 54 steps using pairs, gaps, counts and clues.

Whenever two of the same animal sit side by side, the squares on both ends must be the other animal. Look for these pairs first.

This kind of puzzle is known as a binary or Takuzu puzzle, here with cats and dogs and extra = / × clues.

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