Combinations of string arrays

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Hi there,

I have a string array of length 3. The array is just {"A", "B", "C"}. I have been scratching my head a while in how to possible print out all the combinations for this.

Just to not the size of array can vary so embedding 3 for loops is not a successful solution even though it works great. GRRR.

I want to print out all the 3 letter combos i.e ABC, CAB etc with no letter repition in the output string. There are 6 in total for this case. For others I get the factorial for the array length.

Any suggestions are welcome and thanks in advance for any hel that may be received

Posted 16-Mar-12 11:48am

biki66

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BorysT · Accepted Answer · 2012-03-19T00:40:00

"I want to print out all the 3 letter combos i.e ABC, CAB etc with no letter repition in the output string. There are 6 in total for this case. For others I get the factorial for the array length." aka Permutation.

You can review LINQ+Recursion implementation(a la "smart" multiloop in recursion), like this:

C#

public static IEnumerable<string> GetPermutation(string s)
{
   if (s.Length > 1) {
      return from c in s
             from p in GetPermutation(s.Remove(s.IndexOf(c), 1))
             select c+p;
   } else {
      return new string[] { s };
   }
}

Code from http://stackoverflow.com/questions/774457/combination-generator-in-linq[

CPallini · Accepted Answer · 2012-03-16T12:28:00

Solution 1

Go recursive: recursion would do the job.

Posted 16-Mar-12 12:28pm

CPallini

TRK3 · Accepted Answer · 2012-03-16T12:35:00

If you aren't particularly worried about speed and space issues, the simplest way to do it would be to use recursion.

Basically something on the order of this pseudo-code:

C++

print_all_combinations_of( input_array ) {

   size = input_array.count

   if ( size == 1 ) {
   
       print input_array[0] + "\n"
 
   } else {

       for ( i = 0 ; i < size; i++ ) {

           print input_array[i]

           array_without_element_i = new array( input_array ) 

           array_without_element_i.remove_element_at(i)

           print_all_combinations_of ( array_without_element_i )

       }

   }

}

Combinations of string arrays

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