package Question9_5;
import java.util.*;
public class Question {
public static ArrayList<String> getPerms(String str) {
if (str == null) {
return null;
}
ArrayList<String> permutations = new ArrayList<String>();
if (str.length() == 0) { // base case
permutations.add("");
return permutations;
}
char first = str.charAt(0); // get the first character
String remainder = str.substring(1); // remove the first character
ArrayList<String> words = getPerms(remainder);
for (String word : words) {
for (int j = 0; j <= word.length(); j++) {
String s = insertCharAt(word, first, j);
permutations.add(s);
}
}
return permutations;
}
public static String insertCharAt(String word, char c, int i) {
String start = word.substring(0, i);
String end = word.substring(i);
return start + c + end;
}
public static void main(String[] args) {
ArrayList<String> list = getPerms("abcde");
System.out.println("There are " + list.size() + " permutations.");
for (String s : list) {
System.out.println(s);
}
}
}