293. Flip Game

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LeetCode

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Problem

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.

Example:

Input: s = "++++"
Output:
[
  "--++",
  "+--+",
  "++--"
]

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

Code

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

不要对 string 进行直接修改，比如

x[i] = 'w'

可以使用

s = "hello world"
arr = list(s)
arr[3] = 't'
s_new = "".join(arr)

class Solution:
    def generatePossibleNextMoves(self, s: str) -> List[str]:
        arr = []

        for i in range(0, len(s) - 1):
            if s[i] == '+' and s[i + 1] == '+':
                arr.append(s[:i] + "--" + s[i + 2:])

        return arr