[leetcode]384. Shuffle an Array洗牌

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();

题意：

洗牌

Solution1：

code

class Solution {
    int[] origin;
    int[] nums;
    Random random;

    public Solution(int[] nums) {
        origin = copy(nums);
        this.nums = copy(nums);
        random = new Random();
    }

    /** Resets the array to its original configuration and return it. */
    public int[] reset() {
        nums = copy(origin);
        random = new Random();
        return nums;

    }

    /** Returns a random shuffling of the array. */
    public int[] shuffle() {
        final int n = nums.length;
        int[] result = new int[n];

        for(int i = n; i>=1; i--){
            int randomIdx = random.nextInt(i);
            result[n - i] = nums[randomIdx];
            int temp = nums[randomIdx];
            nums[randomIdx] = nums[i - 1];
            nums[i - 1] = temp;
        }
        return result;
    }

    private int[] copy(int[] array){
        int[] result = new int[array.length];
        for(int i = 0; i < array.length; i++){
            result[i] = array[i];
        }
        return result;
    }
}

/**
 * Your Solution object will be instantiated and called as such:
 * Solution obj = new Solution(nums);
 * int[] param_1 = obj.reset();
 * int[] param_2 = obj.shuffle();
 */