[leetcode] 384. Shuffle an Array

题目

Given an integer array nums, design an algorithm to randomly shuffle the array. All permutations of the array should be equally likely as a result of the shuffling.

Implement the Solution class:

• Solution(int[] nums) Initializes the object with the integer array nums.
• int[] reset() Resets the array to its original configuration and returns it.
• int[] shuffle() Returns a random shuffling of the array.

Example 1:

Input
["Solution", "shuffle", "reset", "shuffle"]
[[[1, 2, 3]], [], [], []]
Output
[null, [3, 1, 2], [1, 2, 3], [1, 3, 2]]

Explanation
Solution solution = new Solution([1, 2, 3]);
solution.shuffle();    // Shuffle the array [1,2,3] and return its result.
                       // Any permutation of [1,2,3] must be equally likely to be returned.
                       // Example: return [3, 1, 2]
solution.reset();      // Resets the array back to its original configuration [1,2,3]. Return [1, 2, 3]
solution.shuffle();    // Returns the random shuffling of array [1,2,3]. Example: return [1, 3, 2]

Constraints:

• 1 <= nums.length <= 200
• -106 <= nums[i] <= 106
• All the elements of nums are unique.
• At most 5 * 104 calls in total will be made to reset and shuffle.

思路

直接调用random.shuffle方法即可。。

代码

python版本：

class Solution:
    def __init__(self, nums: List[int]):
        self.init_nums=nums[:]
        self.nums=nums[:]
        
    def reset(self) -> List[int]:
        self.nums=self.init_nums[:]
        return self.nums

    def shuffle(self) -> List[int]:
        random.shuffle(self.nums)
        return self.nums



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