Find all permutations

Problem

Find all the permutations of a given string whose letters are unique.

Solution

Suppose the string is abcd. Then in its permutations, first letter can be a, b, c or d. If we decide any one of these as the first letter. Then the subproblem arises of having permutations of the rest of the letters. We solve this by recursion.

Code

import java.util.ArrayList;
import java.util.List;

public class FindPermutations
{
 public static void main(String[] args)
 {
  findAllPermutations("abcde");
 }

 private static void findAllPermutations(String string)
 {
  Listcharacters=new ArrayList();
  for(char ch:string.toCharArray())
   characters.add(ch);
  findAllPermutations(new ArrayList(),characters);
 }

 private static void findAllPermutations(List prefix,
   List suffix)
 {
  if(suffix.size()==1)
  {
   for(Character ch:prefix)
    System.out.print(ch);
   System.out.println(suffix.get(0));
   return;
  }
  for(int i=0;i < suffix.size();++i)
  {
   Character ch=suffix.get(i);
   prefix.add(ch);
   suffix.remove(i);
   findAllPermutations(prefix,suffix);
   suffix.add(i,ch);
   prefix.remove(ch);
  }
 }

 
}