CODEWITHSUNDEEP
javaalgorithmcombinations
André Perazzi
André Perazzi

Reputation: 1039

Combining 6 sets of 2 elements in Java

1I'm making a "Virtual Keyboard" for typing passwords in Java.

The password must have 6 numeric chars and each button has 2 possible values. So, there are 2 values possible for each pressed key.

For example: after pressing 6 buttons, I have an array of 6 objects, each one representing the possible values for each character of the password, respectively:

(1 , 5) for char1
(3 , 2) for char2
(7 , 4) for char3
(1 , 5) for char4
(9 , 0) for char5
(8 , 6) for char6

How can I make all combination of 6-digit-strings with these entries? (I guess that would be 64 combinations: 2ˆ6)

Example of valid combinations:

137198
537198
127198
537196

and so on...

Upvotes: 0

Views: 88

Answers (2)

Diogo Ebert
Diogo Ebert

Reputation: 55

Just create every combination possible and check if each of them is the correct one

Upvotes: 1

Giovanni Botta
Giovanni Botta

Reputation: 9816

Given a sequence of n buttons, where each can assume 2 values, this problem reduces to counting from 0 to 2^n-1 since you can interpret each bit at position i as one of the two values that each button can assume. For n=3:

000 -> 137
001 -> 134
010 -> 127
011 -> 124
100 -> 537
...

So just count from 0 to 2^6 and you automatically get your solution.

This is the same way you would go about generating the 2^n subsets of a set of n elements.

Upvotes: 2

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