Question

190

get all combinations for a string

rated 0 times [ 192] [ 2] / answers: 1 / hits: 31130 / 12 Years ago, tue, august 21, 2012, 12:00:00

I'm trying to create a function in JavaScript that given a string will return an array of all possible combinations of the letters with each used at most once, starting with the shortest. e.g for the string ABC it would return:

A

B

C

AB

AC

ABC

I could use loops like so:

for(i=0; i<string.length; i++) {

   //add string[i]

}

for(i=0; i<string.length; i++) {

    for(a=i; a<string.length; a++) {

            //add string[i]+string[a]

    }

}

for(i=0; i<string.length; i++) {

    for(a=i; a<string.length; a++) {

        for(b=a; b<string.length; b++) {

            //add string[i]+string[a]+string[b]

        }

    }

}

But I don't know the length of the string, so wouldn't know how many loops to use.

Any ideas?

Edit: I'm not asking for permutations, abc and acb shouldn't both be returned. Also the shortest being first in the array is important.

This is not homework. It's for a program to solve a 'lights-out' type game.

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jonrened

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2 Years ago

answered 12 Years ago ronniem · Accepted Answer

This is what I ended up using.

var combinations = function (string)

{

    var result = [];



    var loop = function (start,depth,prefix)

    {

        for(var i=start; i<string.length; i++)

        {

            var next = prefix+string[i];

            if (depth > 0)

                loop(i+1,depth-1,next);

            else

                result.push(next);

        }

    }



    for(var i=0; i<string.length; i++)

    {

        loop(0,i,'');

    }



    return result;

}