文章作者：Tyan
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1. Description

Random Flip Matrix

2. Solution

解析：Version 1，使用單一數字作為矩陣的坐標索引，利用字典來保存訪問過的矩陣索引，如果隨機得到的索引在字典中存在，則繼續(xù)進行隨機索引，直至找到一個未訪問過的索引，如果所有索引都訪問過，則返回空坐標。

• Version 1

class Solution:

    def __init__(self, m: int, n: int):
        self.m = m
        self.n = n
        self.coordinates = m * n
        self.visited = {}


    def flip(self) -> List[int]:
        if len(self.visited) == self.coordinates:
            return []
        index = random.randrange(self.coordinates)
        while index in self.visited:
            index = random.randrange(self.coordinates)
        self.visited[index] = 1
        return [index // self.n, index % self.n]


    def reset(self) -> None:
        self.visited = {}


# Your Solution object will be instantiated and called as such:
# obj = Solution(m, n)
# param_1 = obj.flip()
# obj.reset()

Reference

1. https://leetcode.com/problems/random-flip-matrix/