解法1： O(N), Fisher-Yates Algorithm
参看这个geeksforgeeks的文章
384. Shuffle an Array
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class Solution {
int[] data = null;
int[] backup = null;
Random random;
public Solution(int[] nums) {
data = nums;
backup = Arrays.copyOf(data, data.length);
random = new Random(System.currentTimeMillis());
}
/** Resets the array to its original configuration and return it. */
public int[] reset() {
data = Arrays.copyOf(backup, backup.length);
return data;
}
/** Returns a random shuffling of the array. */
public int[] shuffle() {
for (int i = data.length - 1; i > 0; i--) {
int pick = random.nextInt(i + 1);
swap(i, pick);
}
return data;
}
private void swap(int i, int j) {
int temp = data[i];
data[i] = data[j];
data[j] = temp;
}
}
/**
* 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();
*/