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Kode #97: hints & solution

Here's the clue board for Kode #97. Start with the spoiler-free hints. If you're still stuck, the full step-by-step solution is below, hidden until you open it.

The clue board

Each row is a guess that's already been graded. ▲ means a right digit in the right spot; ● means a right digit in the wrong spot.

  • 18175▲1●1
  • 28463▲0●2
  • 32103▲1●1
  • 43542▲0●2
  • 50827▲0●0

Spoiler-free hints

  • Exactly one of the four digits is even.
  • The four digits add up to 15.
  • 2 of the digits are 5 or higher.

Try the hints first. The solution below walks through every deduction.

Step-by-step solution

Every Kode can be cracked by pure deduction, with no guessing. This board falls in 11 logical steps. Open the solution to follow them one at a time.

Show the solution · reveals the code

When a row "rules out" a position, it shows that digit there but its ▲ marks are already used up (or it has none), so the digit can't sit there.

  1. Row 5 (0 8 2 7) has no marks at all, so 0, 8, 2, and 7 are not in the code.
  2. Row 1 (8 1 7 5) has 2 marks still unexplained, and only 2 digits are left undecided: 1 and 5. So both are in the code.
  3. Row 3 (2 1 0 3) has one mark still unexplained, and only one digit is left undecided: 3. So it is in the code.
  4. Row 4 (3 5 4 2) has 2 marks, already accounted for by 3 and 5. That rules out 4.
  5. Row 2 (8 4 6 3) has one mark still unexplained, and only one digit is left undecided: 6. So it is in the code.
  6. That makes all four digits of the code: 1, 3, 5, and 6. Every other digit is out, which also rules out 9.
  7. Row 3 (2 1 0 3) has one digit in the right spot. Since row 2 rules out the 3 in position 4, it has to be the 1 in position 2.
  8. Row 1 (8 1 7 5) has only one digit in the right spot, already accounted for by the 1 in position 2. So the 5 isn't in position 4.
  9. The 3 has only one spot left: position 3 (row 4 rules out position 1, row 2 rules out position 4, and position 2 is already 1).
  10. The 5 has only one spot left: position 1 (row 1 rules out position 4, position 2 is already 1, and position 3 is already 3).
  11. That leaves the 6 for position 4.

That cracks it: the code is 5136.

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