Flip Game

You are playing the following Flip Game with your friend: Given a string that contains only these two characters: 

+

 and 

-

,
you and your friend take turns to flip two consecutive 

"++"

 into 

"--"

.
The game ends when a person can no longer make a move and therefore the other person will be the winner.

Write a function to compute all possible states of the string after one valid move.

For example, given 

s = "++++"

, after one move, it may become one of the following states:

[
"--++",
"+--+",
"++--"
]

思路：就是记录每个状态，记得翻转回来，然后再继续即可。
public class Solution {
public List<String> generatePossibleNextMoves(String s) {
List<String> list = new ArrayList<String>();
if(s == null || s.length() == 0) return list;
char[] chars = s.toCharArray();
for(int i=0; i<chars.length-1; i++){
if(chars[i]=='+' && chars[i+1]=='+'){
chars[i] = '-';
chars[i+1] = '-';
list.add(new String(chars));
chars[i] = '+';
chars[i+1] = '+';
}
}
return list;
}
}