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:

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

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

Solution

public class Solution {
    public List<String> generatePossibleNextMoves(String s) {
        List<String> ans = new ArrayList<String>();
        char ss[] = s.toCharArray();
        for(int i = 1; i < s.length(); i++) {
            if(ss[i-1]=='+'&&ss[i]=='+') {
                ss[i-1]='-';
                ss[i]='-';
                ans.add(new String(ss));
                ss[i-1]='+';
                ss[i]='+';
            }
        }
        return ans;
    }
}