384. Shuffle an Array

最新推荐文章于 2020-04-12 08:34:05 发布

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本文介绍了一个用于随机打乱不含重复元素数组的算法实现，并通过一个具体示例进行说明。该算法能够确保每次打乱后的数组元素顺序不同且等概率出现。

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();

多次提交失败都是因为大数据测试下概率不平均，所以概率随机很重要

public class Solution {
	private int array[];
	private int output[];

	public Solution(int[] nums) {
		array = nums;
		output = new int[nums.length];
	}

	/** Resets the array to its original configuration and return it. */
	public int[] reset() {
		return array;
	}

	/** Returns a random shuffling of the array. */
	public int[] shuffle() {
		for (int i = 0; i < array.length; i++) {
			output[i] = array[i];
		}
		Random r = new Random();
		for (int i = output.length - 1; i >= 0; i--) {
			int random = r.nextInt(i+1);
			int tmp = output[i];
			output[i] = output[random];
			output[random] = tmp;
		}			
		return output;
	}
}