# 384. Shuffle an Array

Medium
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 <= 50`
• `-10^6 <= nums[i] <= 10^6`
• All the elements of `nums` are unique.
• At most `10^4` calls in total will be made to `reset` and `shuffle`.

### 解題

type Solution struct {
arr []int
}
func Constructor(nums []int) Solution {
return Solution{ arr: nums }
}
func (this *Solution) Reset() []int {
return this.arr
}
func (this *Solution) Shuffle() []int {
a := make([]int, len(this.arr))
copy(a, this.arr)
rand.Seed(time.Now().UnixNano())
rand.Shuffle(len(a), func(i, j int) { a[i], a[j] = a[j], a[i] })
return a
}
/**
* Your Solution object will be instantiated and called as such:
* obj := Constructor(nums);
* param_1 := obj.Reset();
* param_2 := obj.Shuffle();
*/