Flip Game

Leetcode

題意：

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 [].

解題思路：

兩兩判斷，若兩個同時為'+'時，把兩個轉為'-'，再加入res中。

public class Solution {
    public List<String> generatePossibleNextMoves(String s) {

        List<String> res = new ArrayList<String>();

        if (s == null || s.length() == 0) {
            return res;
        }
        char[] original = s.toCharArray();
        for (int i = 0; i < original.length - 1; i++) {
            if (original[i] == '+' && original[i + 1] == '+') {
                original[i] = '-';
                original[i + 1] = '-';
                res.add(new String(original));
                original[i] = '+';
                original[i + 1] = '+';
            }
        }

        return res;
    }
}