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leetcode mock Shuffle an Array

1. shuffle算法:

http://www.cnblogs.com/huaping-audio/archive/2008/09/09/1287985.html

注意:我们一般用的是第二种swap的方法;但是第一种直接选择,然后把最末尾一位填上的方法,也是很好的。只是会需要两倍的空间。

 

2. Random nextInt(bound)参数表示 0-inclusive,bound-exclusive: [0, bound)

 

package com.company;import java.util.LinkedList;import java.util.List;import java.util.Random;public class Main {    private int[] orig;    public Main(int[] nums) {        orig = nums;    }    /** Resets the array to its original configuration and return it. */    public int[] reset() {        return orig;    }    /** Returns a random shuffling of the array. */    public int[] shuffle() {        int[] ret = orig.clone();        Random rand = new Random();        for (int i=0; i<ret.length; i++) {            // int value between 0 (inclusive) and the specified value (exclusive)            int r = rand.nextInt(ret.length-i);            if (r != ret.length-i-1) {                int k = ret[r];                ret[r] = ret[ret.length - i - 1];                ret[ret.length - i - 1] = k;            }        }        return ret;    }    public static void main(String[] args) {        // write your code here        System.out.println("Hello");        int []nums = {1,2,3};        Main obj = new Main(nums);        int[] param_1 = obj.reset();        int[] param_2 = obj.shuffle();        System.out.printf("param_1: %d, %d, %d\n", param_1[0], param_1[1], param_1[2]);        System.out.printf("param_2: %d, %d, %d\n", param_2[0], param_2[1], param_2[2]);    }}

 

leetcode mock Shuffle an Array