293. Flip Game

• Difficulty: Easy

• Topics: String

• Similar Questions:

  • Flip Game II

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 [].

Solutions:

class Solution {
public:
    vector<string> generatePossibleNextMoves(string s) {
        vector<string> ret;
        for (int i = 0; i < int(s.length() - 1) ; ++i) { // caution!!!!
            if (s[i] == '+' && s[i + 1] == '+') {
                s[i] = '-';
                s[i + 1] = '-';
                ret.push_back(s);
                s[i + 1] = '+';
                s[i] = '+';
            }
        }

        return ret;
    }
};