string reorder

Time Limit: 10000ms
Case Time Limit: 1000ms
Memory Limit: 256MB

Description

For this question, your program is required to process an input string containing only ASCII characters between ‘0’ and ‘9’, or between ‘a’ and ‘z’ (including ‘0’, ‘9’, ‘a’, ‘z’). 

Your program should reorder and split all input string characters into multiple segments, and output all segments as one concatenated string. The following requirements should also be met,
1. Characters in each segment should be in strictly increasing order. For ordering, ‘9’ is larger than ‘0’, ‘a’ is larger than ‘9’, and ‘z’ is larger than ‘a’ (basically following ASCII character order).
2. Characters in the second segment must be the same as or a subset of the first segment; and every following segment must be the same as or a subset of its previous segment. 

Your program should output string “<invalid input string>” when the input contains any invalid characters (i.e., outside the '0'-'9' and 'a'-'z' range).

Input

Input consists of multiple cases, one case per line. Each case is one string consisting of ASCII characters.

Output

For each case, print exactly one line with the reordered string based on the criteria above.


Sample In

aabbccdd
007799aabbccddeeff113355zz
1234.89898
abcdefabcdefabcdefaaaaaaaaaaaaaabbbbbbbddddddee


Sample Out

abcdabcd
013579abcdefz013579abcdefz
<invalid input string>

abcdefabcdefabcdefabdeabdeabdabdabdabdabaaaaaaa

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

public class Main {
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		List<String> stringList = new ArrayList<String>();
		for (int i = 0; i < 4; i++) {
			stringList.add(in.nextLine());
		}
		System.out.println("================");
		for (String string : stringList) {
			for (int i = 0; i < string.length(); i++) {
				if (!((string.charAt(i) >= '0' && string.charAt(i) <= '9') || (string
						.charAt(i) >= 'a' && string.charAt(i) <= 'z'))) {
					System.out.println("<invalid input string>");
					break;
				}
				if (i == string.length() - 1) {
					process(string);
				}
			}
		}
	}

	private static void process(String string) {
		//System.out.println("after: " + sort(string));
		String sortedString = sort(string);
		List<Character> charList = new ArrayList<Character>();
		
		List<Character> deleteCharList = new ArrayList<Character>();
		for (int i = 0; i < sortedString.length(); i++) {
			char ch = sortedString.charAt(i);
			charList.add(ch);
		}
		while (!charList.isEmpty()) {
			List<Character> newCharList = new ArrayList<Character>();
			for (Character ch : charList) {
				if (!newCharList.contains(ch)) {
					newCharList.add(ch);
				}
			}
			//printList(newCharList);
			deleteCharList.addAll(newCharList);
			for (Character character : newCharList) {
				charList.remove(character);
			}
			//printList(charList);
		}
		printList(deleteCharList);
	}

	private static void swap(char[] chars, int a, int b) {
		char temp = chars[a];
		chars[a] = chars[b];
		chars[b] = temp;
	}

	private static String sort(String string) {
		char[] chars = string.toCharArray();
		for (int i = 0; i < chars.length - 1; i++) {
			for (int j = i + 1; j < chars.length; j++) {
				if (chars[j] < chars[i]) {
					swap(chars, i, j);
				}
			}
		}
		return new String(chars);
	}

	private static void printList(List<Character> list) {
		for (Character character : list) {
			System.out.print(character);
		}
		System.out.println();
	}
}