// Allison Obourn
// CSE 143 - lecture 18
// Demonstrates an exhaustive search algorithm by generating all permutations of 
// a given string.
public class Permutations {
   public static void main(String[] args) {
      permute("team");
   }

   // Outputs all permutations of the given string, one per line.
   // For example, TEAM can be permuted into MEAT, META, TMEA, ...
   public static void permute(String s) {
      permute(s, "");
   }
   
   // Outputs all permutations of a string
   private static void permute(String s, String chosen) {
      if(s.length() == 0) {
         System.out.println(chosen);
      } else {
         for(int i = 0; i < s.length(); i++) {
            // when we use primitive types or Strings, we can choose and
            // unchoose simply by passing a copy of the value to recursive
            // calls.
            char c = s.charAt(i);
            // chosen += c; // explicit "choose"
            String temp = s.substring(0, i) + s.substring(i + 1);
            
            permute(temp, chosen + c);
            
            // explicit unchoose if we modify chosen and s:
            // s = s.substring(0, i) + c + s.substring(i);
            // chosen = chosen.substring(0, chosen.length() - 1);
         }
      }
   }

}