Reverse List String

/*
 * Author: Yang Pei
 * Problem: Reverse List String
 * 
 * Note:
 * Given a string represent by a list, each node in the list contains a character,
 * A word is separated by space. Reverse each word in the list.
 * For example
 * 'h'->'e'->'l'->'l'->'o'->' '->'w'->'o'->'r'->'l'->'d' would be changed to
 * 'o'->'l'->'l'->'e'->'h'->' '->'d'->'l'->'r'->'o'->'w'
 * 
 * Solution:
 * Two pointers. Be careful: there might be multiple spaces between two words. And there
 * might be leading and tailing spaces. And there might contains no space and there might 
 * be all space.
 * 
 * Define of the ListNodeC 
 * {
 *     char val;
 *     ListNodeC next;
 *     public ListNodeC(char ch) {
 *         this.val = ch;
 *         this.next = null;
 *     }
 * }
 */
public class ReverseListString {
    public static ListNodeC reverse(ListNodeC head) {
        if(head == null) 
            return head;
        ListNodeC dummy = new ListNodeC(' ');
        dummy.next = head;
        ListNodeC pointer1 = dummy, pointer2 = dummy;
        while(pointer1.next != null) {
            while(pointer2.next != null && pointer2.next.val == ' ')
                pointer2 = pointer2.next;
            if(pointer2.next == null)
                break;
            pointer1 = pointer2;
            // pay attention here, otherwise would have infinite loop
            pointer2 = pointer2.next;
            while(pointer2.next != null && pointer2.next.val != ' ') {
                ListNodeC temp = pointer2.next;
                pointer2.next = temp.next;
                temp.next = pointer1.next;
                pointer1.next = temp;
            }
            pointer1 = pointer2;
        }
        return dummy.next;
    }
    
    public static void main(String[] args) {
        String str = " a ba   c  ";
        ListNodeC dummy = new ListNodeC(' ');
        ListNodeC temp = dummy;
        for(int i = 0; i < str.length(); i++) {
            ListNodeC node = new ListNodeC(str.charAt(i));
            temp.next = node;
            temp = temp.next;
        }
        temp = dummy.next;
        while(temp != null) {
            System.out.print(temp.val);
            temp = temp.next;
        }
        System.out.println("");
        temp = reverse(dummy.next);
        while(temp != null) {
            System.out.print(temp.val);
            temp = temp.next;
        }
        System.out.println("");
    }
}