permutations

[chandru50]

pl. help.

write a Cprogramme to find all permutations ( a string of given characters)

[DeMan]

I forget which is combinations and which is permutations but I think (and correct me if I'm wrong), that permutations are all the different ways we can create a string of n characters from a string of m (>n) characters. The difficulty is if the characters are not unique (because CC and CC are indistinguishable) - Assuming, then (because it's easier) that you have a string of unique characters the method would be something like (There may be some bugs uin my thinking, but at least this should give some idea):

{
  Get String from user.
  Get permutation length from user:
  Check perm length > String length;
  startPermutations("",input, length);
}
 
startPermutations(String, soFar, String input, int length)
{
  if (length=0)
  {
    print soFar;
  }
  else
  {
    for(number of  character in the String)
    {
      soFar=soFar+currentChar;
      input=input.subString(1, input.length);
      startPermutations(soFar, input, length -1);
      move currentChar to back of String, so we can repeat with the next;
    }
  }
}