I'm trying to solve a lock 3 code game, Can You Crack The Code. From time to time I find myself presented with a puzzle that has 2 possible solutions, but the game only allows one correct answer. For example, in the puzzle shown below, the possibilities I narrowed down are:

8 1 0   or   8 0 9

and I can't figure out which one is correct.


How do I know which answer to give?

  • 3
    $\begingroup$ Hello and welcome to PSE! I'd advise you to read the tour page. Further, puzzles taken from elsewhere must provide an attribution to the original source, or they risk being deleted. $\endgroup$
    – Phylyp
    Feb 4, 2018 at 5:58
  • 1
    $\begingroup$ Possible duplicate of Crack the lock code only numbers are diffrerent, even text is the same. $\endgroup$
    – Oray
    Feb 4, 2018 at 9:58
  • $\begingroup$ Thanks for the feedback, the puzzle is taken from a game play.google.com/store/apps/… and as Oray said i found the same post wich is the same game. ive been trying to make a javascript solver for this code because the game repeats the rules and only changes the numbers. but there are certain conbinations that i get 2 results possibles. $\endgroup$ Feb 4, 2018 at 18:31
  • $\begingroup$ from the answer provided by jonMark im stuck in the same problem. $\endgroup$ Feb 4, 2018 at 18:37
  • 1
    $\begingroup$ @SebastianCardenas You should edit the attribution into the puzzle post. If the game presents this puzzle as shown, with the guesses already pre-filled, and you're supposed to use them to solve the code, then you should explain that as well (it's not obvious from the post if those were game-supplied or player-supplied guesses). If pre-filled, this game is bad—it's not possible to determine, short of by guessing, which of the equally valid possibilities is intended. $\endgroup$
    – Rubio
    Feb 4, 2018 at 21:49

4 Answers 4


Clues 1 and 5 tell you 8 is in the answer. Clue 2 puts 8 first, and with clues 3 and 4, we know 0 is in the answer. Clue 5 says one of the others is 1 or 9, and you are right - there isn't enough information to decide between 809 and 810.


I've concluded that

Two answers are valid:
  - 810
  - 809

Summarizing the 5 conidtions (the 5 boxes) where rows are the possible numbers. x means not a valid digit at the given place for sure.
X/Y means X of the Y cases. Light green: possible digit Light red: possible "not"

enter image description here

It reduces the the options for the first 3 conditions:
enter image description here

Based on the 419 condition we can go with:
  1. ?1?
  2. ??9
enter image description here

Let's see the ?1? branch: 9 is out then:
enter image description here

Gives two options:81? or ?18:
enter image description here

81? leads to 810 which works:
enter image description here

?18 leads to conflict:
enter image description here

The ??9 branch: number 1 is out, then 8?9 then 809:
enter image description here

Also this method proves that no other solutions exists.
Yellow: the new changes
Gray: changes due to new changes
Blue: number and place identified
Red: conflict

  • $\begingroup$ 839 conflicts with clue #2. 319 conflicts with clue #1. $\endgroup$
    – JS1
    Dec 20, 2019 at 23:41
  • $\begingroup$ Yes, I've realized this as well. TY. Corrected. $\endgroup$
    – SmileAdm
    Dec 21, 2019 at 10:42

The answer is:



547 is not in code then 1,9,3,8,0 comes 3 is not beacause it is wrong placed and last code is 809 is correct


809 is the answer. The first clue states that "one number is correct and well placed", and the first clue was occupied by 9, so 809 is the answer.

  • 2
    $\begingroup$ That ... doesn't exclude the other possibility at all. 810 also would have one number is correct and well placed. $\endgroup$
    – Rubio
    Apr 8, 2018 at 22:25

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