LeetCode 294. Flip Game II（反转游戏II）

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本文探讨了LeetCode上Flip Game II的问题解决方法，通过MinMax算法及深度优先搜索策略，帮助玩家确定是否能确保赢得游戏。文章提供了详细的代码实现。

原题网址：https://leetcode.com/problems/flip-game-ii/

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 twoconsecutive "++" 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 determine if the starting player can guarantee a win.

For example, given s = "++++", return true. The starting player can guarantee a win by flipping the middle "++" to become "+--+".

Follow up:
Derive your algorithm's runtime complexity.

方法：MinMax算法，深度优先搜索

public class Solution {
    private boolean canWin(char[] sa) {
        for(int i=0; i<sa.length-1; i++) {
            if (sa[i]=='+' && sa[i+1]=='+') {
                sa[i]='-';
                sa[i+1]='-';
                boolean otherCanWin = canWin(sa);
                sa[i]='+';
                sa[i+1]='+';
                if (!otherCanWin) return true;
            }
        }
        return false;
    }
    public boolean canWin(String s) {
        return canWin(s.toCharArray());
    }
}

这道题有个很牛的算法，我没看懂。。。

参考：

https://leetcode.com/discuss/64344/theory-matters-from-backtracking-128ms-to-dp-0ms

http://www.1point3acres.com/bbs/thread-144510-1-1.html

http://www.1point3acres.com/bbs/thread-137953-1-1.html