293. Flip Game

Link

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 twoconsecutive "++" 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:

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

If there is no valid move, return an empty list [].

public static List<String> generatePossibleNextMoves(String s) {
    List<String> ret = new ArrayList<>();
    char[] chars = s.toCharArray();
    int len = chars.length;
    int i = 0, j = 1;
    while(j < len){
        if(chars[i] == chars[j] && chars[i] == '+'){
            chars[i] = '-';
            chars[j] = chars[i];
            ret.add(new String(chars));
            chars[i] = '+';
            chars[j] = chars[i];
        }
        i++;
        j++;
    }
    return ret;
}