Leetcode 293: Flip Game

最新推荐文章于 2021-11-24 14:54:44 发布

dolphin_wby

最新推荐文章于 2021-11-24 14:54:44 发布

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分类专栏： Leetcode 文章标签： String

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本文介绍了一种基于字符串翻转的游戏策略算法。该算法针对包含'+','- '字符的字符串，实现连续两个 '+'字符的有效翻转操作。通过迭代检查字符串元素，找出所有可行的翻转位置，并生成相应的翻转后的字符串状态。

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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 [].

Solution:

Just iterate the string characters and check the element at i and i + 1 are '+'.

Time complexity : O(n)

Space complexity: O(n) (worst)

public class Solution {
    public List<String> generatePossibleNextMoves(String s) {
        List<String> result = new ArrayList<String>();
        for (int i = 0; i < s.length() - 1; i++) {
            if (s.charAt(i) == '+' && s.charAt(i + 1) == '+') {
                String flip = s.substring(0, i) + "--" + s.substring(i + 2);
                result.add(flip);
            }
        }
        return result;
    }
}