[LeetCode]Shuffle an Array

题目描述:

LeetCode 384. Shuffle an Array

Shuffle a set of numbers without duplicates.

Example:

// Init an array with set 1, 2, and 3.
int[] nums = {1,2,3};
Solution solution = new Solution(nums);

// Shuffle the array [1,2,3] and return its result. Any permutation of [1,2,3] must equally likely to be returned.
solution.shuffle();

// Resets the array back to its original configuration [1,2,3].
solution.reset();

// Returns the random shuffling of array [1,2,3].
solution.shuffle();

题目大意:

对一个不包含重复元素的数组执行洗牌操作。

解题思路:

伪代码如下:

for (i = 0 to nums.length)
    swap(nums[randint(0, i)], nums[i])

Python代码:

import random
class Solution(object):

    def __init__(self, nums):
        """
        
        :type nums: List[int]
        :type size: int
        """
        self.nums = nums[:]
        self.base = nums[:]

    def reset(self):
        """
        Resets the array to its original configuration and return it.
        :rtype: List[int]
        """
        self.nums[:] = self.base
        return self.nums

    def shuffle(self):
        """
        Returns a random shuffling of the array.
        :rtype: List[int]
        """
        for x in range(len(self.nums)):
            y = random.randint(0, x)
            self.nums[x], self.nums[y] = self.nums[y], self.nums[x]
        return self.nums


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

 

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