LeetCode [293] 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.

Example:

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

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

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class Solution { public: vector<string> generatePossibleNextMoves(string s) { int n = s.size(); vector<string> ret; for(int i=0; i<n-1; ++i){ if(s.substr(i,2)=="++"){ string tmp = s; tmp[i] = '-'; tmp[i+1] = '-'; ret.push_back(tmp); } } return ret; } };

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//Java class Solution { public List<String> generatePossibleNextMoves(String s) { int n = s.length(); List<String> ret = new ArrayList<>(); for(int i=0; i<n-1; ++i){ StringBuilder sb = new StringBuilder(s); if(sb.substring(i, i+2).equals("++")){ sb.replace(i, i+2, "--"); ret.add(sb.toString()); } } return ret; } }