ShuffleAnArray.py

# -*- coding: utf-8 -*-
# @File    : ShuffleAnArray.py
# @Date    : 2022-07-11
# @Author  : tc
"""
384. 打乱数组
给你一个整数数组 nums ，设计算法来打乱一个没有重复元素的数组。打乱后，数组的所有排列应该是 等可能 的。

实现 Solution class:

Solution(int[] nums) 使用整数数组 nums 初始化对象
int[] reset() 重设数组到它的初始状态并返回
int[] shuffle() 返回数组随机打乱后的结果

示例 1：
输入
["Solution", "shuffle", "reset", "shuffle"]
[[[1, 2, 3]], [], [], []]
输出
[null, [3, 1, 2], [1, 2, 3], [1, 3, 2]]

解释
Solution solution = new Solution([1, 2, 3]);
solution.shuffle();    // 打乱数组 [1,2,3] 并返回结果。任何 [1,2,3]的排列返回的概率应该相同。例如，返回 [3, 1, 2]
solution.reset();      // 重设数组到它的初始状态 [1, 2, 3] 。返回 [1, 2, 3]
solution.shuffle();    // 随机返回数组 [1, 2, 3] 打乱后的结果。例如，返回 [1, 3, 2]

Fisher-Yates 洗牌算法:
https://leetcode.cn/problems/shuffle-an-array/solution/da-luan-shu-zu-yi-ding-gong-ping-de-xi-p-21iy/

"""
import random
from typing import List

class Solution:
    def __init__(self, nums: List[int]):
        self.nums = nums
        self.original = nums.copy()

    def reset(self) -> List[int]:
        self.nums = self.original.copy()
        return self.nums

    def shuffle(self) -> List[int]:
        shuffled = [0] * len(self.nums)
        for i in range(len(self.nums)):
            j = random.randrange(len(self.nums))
            shuffled[i] = self.nums.pop(j)
        self.nums = shuffled
        return self.nums

# Your Solution object will be instantiated and called as such:
# obj = Solution(nums)
# param_1 = obj.reset()
# param_2 = obj.shuffle()