依旧排列组合问题

public static void arragments(int[] a, int first, int num)
	{
		if(num == 0)
		{
			for(int i : a)
			{
				System.out.print(i);
			}
			System.out.println();
			return;
		}
		for(int i = first; i < first + num; i++)
		{
			swap(a, i, first);
			arragments(a, first + 1, num - 1);
			swap(a, first, i);
		}
	}
	
	private static void swap(int[] a, int i, int first) {
		int temp = a[i];
		a[i] = a[first];
		a[first] = temp;
	}


	public static List findAllArrangment(String input)
	{
		List<String> result = new ArrayList<String>();
		if(input.length() == 0)
		{
			result.add("");
			return result;
		}
		else
		{
			char a = input.charAt(0);
			List<String> subResult = new ArrayList<String>();
			String remain = input.substring(1);
			subResult = findAllArrangment(remain);
			for(String s : subResult)
			{
				for (int j = 0; j <= s.length(); j++) {
					result.add(insertCharAt(s, a, j));
				}
			}
			return result;
		}

	}
	
	
	public static List findAllCombination(String input)
	{
		List<String> result;
		if(0 == input.length())
		{
			result = new ArrayList();;
			result.add(new String(""));
			return result;
		}
		else
		{
			char c = input.charAt(0);
			String remain = input.substring(1);
			result = findAllCombination(remain);
			List<String> moreResult = new ArrayList();;
			for(String s : result)
			{
				moreResult.add(s+c);
			}
			result.addAll(moreResult);
			return result;
		}
	
	}
	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;
	}