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();
 */