我需要随机洗牌以下数组:
int[] solutionArray = {1, 2, 3, 4, 5, 6, 6, 5, 4, 3, 2, 1};
有什么函数可以做到吗?
我需要随机洗牌以下数组:
int[] solutionArray = {1, 2, 3, 4, 5, 6, 6, 5, 4, 3, 2, 1};
有什么函数可以做到吗?
当前回答
Collections类有一个有效的洗牌方法,可以复制,这样就不依赖于它:
/**
* Usage:
* int[] array = {1, 2, 3};
* Util.shuffle(array);
*/
public class Util {
private static Random random;
/**
* Code from method java.util.Collections.shuffle();
*/
public static void shuffle(int[] array) {
if (random == null) random = new Random();
int count = array.length;
for (int i = count; i > 1; i--) {
swap(array, i - 1, random.nextInt(i));
}
}
private static void swap(int[] array, int i, int j) {
int temp = array[i];
array[i] = array[j];
array[j] = temp;
}
}
其他回答
下面是一个有效的Fisher-Yates shuffle数组函数:
private static void shuffleArray(int[] array)
{
int index;
Random random = new Random();
for (int i = array.length - 1; i > 0; i--)
{
index = random.nextInt(i + 1);
if (index != i)
{
array[index] ^= array[i];
array[i] ^= array[index];
array[index] ^= array[i];
}
}
}
or
private static void shuffleArray(int[] array)
{
int index, temp;
Random random = new Random();
for (int i = array.length - 1; i > 0; i--)
{
index = random.nextInt(i + 1);
temp = array[index];
array[index] = array[i];
array[i] = temp;
}
}
下面是一个使用数组列表的简单方法:
List<Integer> solution = new ArrayList<>();
for (int i = 1; i <= 6; i++) {
solution.add(i);
}
Collections.shuffle(solution);
使用集合来洗牌一个基本类型数组有点过分……
你自己实现这个函数很简单,比如使用Fisher-Yates shuffle:
import java.util.*;
import java.util.concurrent.ThreadLocalRandom;
class Test
{
public static void main(String args[])
{
int[] solutionArray = { 1, 2, 3, 4, 5, 6, 16, 15, 14, 13, 12, 11 };
shuffleArray(solutionArray);
for (int i = 0; i < solutionArray.length; i++)
{
System.out.print(solutionArray[i] + " ");
}
System.out.println();
}
// Implementing Fisher–Yates shuffle
static void shuffleArray(int[] ar)
{
// If running on Java 6 or older, use `new Random()` on RHS here
Random rnd = ThreadLocalRandom.current();
for (int i = ar.length - 1; i > 0; i--)
{
int index = rnd.nextInt(i + 1);
// Simple swap
int a = ar[index];
ar[index] = ar[i];
ar[i] = a;
}
}
}
无随机解:
static void randomArrTimest(int[] some){
long startTime = System.currentTimeMillis();
for (int i = 0; i < some.length; i++) {
long indexToSwap = startTime%(i+1);
long tmp = some[(int) indexToSwap];
some[(int) indexToSwap] = some[i];
some[i] = (int) tmp;
}
System.out.println(Arrays.toString(some));
}
使用ArrayList<Integer>可以帮助您解决洗牌问题,而无需应用大量逻辑和消耗更少的时间。以下是我的建议:
ArrayList<Integer> x = new ArrayList<Integer>();
for(int i=1; i<=add.length(); i++)
{
x.add(i);
}
Collections.shuffle(x);