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ShuffleAnArray.java
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ShuffleAnArray.java
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package com.hncboy;
import java.util.Arrays;
import java.util.Random;
/**
* @author hncboy
* @date 2019/10/9 8:46
* @description 384.打乱数组
*
* 给你一个整数数组 nums ,设计算法来打乱一个没有重复元素的数组。
* 实现 Solution class:
* Solution(int[] nums) 使用整数数组 nums 初始化对象
* int[] reset() 重设数组到它的初始状态并返回
* int[] shuffle() 返回数组随机打乱后的结果
*
* 示例:
* 输入
* ["Solution", "shuffle", "reset", "shuffle"]
* [[[1, 2, 3]], [], [], []]
* 输出
* [null, [3, 1, 2], [1, 2, 3], [1, 3, 2]]
* 解释
* Solution solution = new Solution([1, 2, 3]);
* solution.shuffle(); // 打乱数组 [1,2,3] 并返回结果。任何 [1,2,3]的排列返回的概率应该相同。例如,返回 [3, 1, 2]
* solution.reset(); // 重设数组到它的初始状态 [1, 2, 3] 。返回 [1, 2, 3]
* solution.shuffle(); // 随机返回数组 [1, 2, 3] 打乱后的结果。例如,返回 [1, 3, 2]
*
* 提示:
* 1 <= nums.length <= 200
* -106 <= nums[i] <= 106
* nums 中的所有元素都是 唯一的
* 最多可以调用 5 * 104 次 reset 和 shuffle
*
* 来源:力扣(LeetCode)
* 链接:https://leetcode-cn.com/problems/shuffle-an-array
* 著作权归领扣网络所有。商业转载请联系官方授权,非商业转载请注明出处。
*/
public class ShuffleAnArray {
public static void main(String[] args) {
int[] nums = new int[]{1, 2, 3};
Solution solution = new Solution(nums);
System.out.println(Arrays.toString(solution.shuffle()));
System.out.println(Arrays.toString(solution.reset()));
}
private static class Solution {
private final int n;
private final int[] nums;
private Random random = new Random();
public Solution(int[] nums) {
this.nums = nums;
n = nums.length;
}
public int[] reset() {
return nums;
}
public int[] shuffle() {
int[] result = nums.clone();
for (int i = 0; i < n; i++) {
swap(result, i, i + random.nextInt(n - i));
}
return result;
}
private void swap(int[] array, int i, int j) {
int temp = array[i];
array[i] = array[j];
array[j] = temp;
}
}
}