Career cup 9.5

StringPermutation.java

package Chapter9;

import java.util.ArrayList;

public class StringPermutation {
    public static ArrayList<String> getAllPermutations(String s) {
	ArrayList<String> permutations = new ArrayList<>();
	permutations.add("");
	for(int i = 0; i < s.length(); i++) {
	    char c = s.charAt(i);
	    ArrayList<String> newPermutations = new ArrayList<String>();
	    for (String perm : permutations) {
		for(int j = 0; j <= perm.length(); j++) {
		    newPermutations.add(perm.substring(0, j) + c + perm.substring(j));
		}
	    }
	    permutations = newPermutations;
	    newPermutations = null;
	}
	return permutations;
    }
    
    public static void printPerms(ArrayList<String> perms) {
	for (String perm : perms) {
	    System.out.println(perm);
	}
	System.out.println("total " + perms.size() +" permutations");
    }
    
    public static void main(String[] args) {
	String testString = "HelloWorld";
	printPerms(getAllPermutations(testString));
    }
}