Get all possible combinations of characters in an array

Question

I have an array of characters c[][] with different mappings to each index. For example:

{'a', 'b', 'c', 'd', 'e', 'f' } {'g', 'h', 'i' }

I need to return all the possible character combinations for this array as a string. That meaning, for the above character array, I should return: "ag", "ah", "ai", "bg", "bh", "bi", "cg", "ch", "ci", etc. It would be easy to do this for a character array of only two things like above, but if there are more arrays, then I do not know what to do... Which is what I am asking you all to help me with! :)

check out http://stackoverflow.com/questions/2920315/permutation-of-array — JKirchartz, Mar 01 '12 at 18:24
What depth does the array have? That is to say how many dimentions? — , Mar 01 '12 at 18:24

score 11 · Accepted Answer · answered Mar 01 '12 at 18:26

11

For two arrays two nested loops should do:

for (int i = 0 ; i != c[0].length ; i++) {
    for (int j = 0 ; j != c[1].length ; j++) {
        System.out.writeln(""+c[0][i]+c[1][j]);
    }
}

For more nesting you would need a recursive or an equivalent stack-based solution.

void combos(int pos, char[][] c, String soFar) {
    if (pos == c.length) {
         System.out.writeln(soFar);
         return;
    }
    for (int i = 0 ; i != c[pos].length ; i++) {
        combos(pos+1, c, soFar + c[pos][i]);
    }
}

Call this recursive function from your main() like this:

combos(0, c, "");

answered Mar 01 '12 at 18:26

Sergey Kalinichenko

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Ah, I should have realized this. :p Thanks for the help! Really nice code. – Supervisor Mar 02 '12 at 01:04
@Supervisor You are welcome! If the answer works for you, consider [accepting it](http://meta.stackexchange.com/questions/16721/how-does-accept-rate-work) to indicate that the problem is solved, and to earn yourself a brand-new badge on Stack Overflow. – Sergey Kalinichenko Mar 02 '12 at 02:23

Get all possible combinations of characters in an array

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