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:

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

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

Tips:

很简单啦，注意charAt后面用==而不是.equals()和substring的index就好

Code:

public class Solution {
    public List<String> generatePossibleNextMoves(String s) {
        List<String> result = new ArrayList<>();
        for (int i = 1; i < s.length(); i++) {
            if (s.charAt(i - 1) == '+'  && s.charAt(i) =='+'){
                result.add(s.substring(0, i - 1) + "--" + s.substring(i + 1, s.length()));
            }
        }
        return result;
    }
}