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
使用随机类
public static void randomizeArray(int[] arr) {
Random rGenerator = new Random(); // Create an instance of the random class
for (int i =0; i< arr.length;i++ ) {
//Swap the positions...
int rPosition = rGenerator.nextInt(arr.length); // Generates an integer within the range (Any number from 0 - arr.length)
int temp = arr[i]; // variable temp saves the value of the current array index;
arr[i] = arr[rPosition]; // array at the current position (i) get the value of the random generated
arr[rPosition] = temp; // the array at the position of random generated gets the value of temp
}
for(int i = 0; i<arr.length; i++) {
System.out.print(arr[i]); //Prints out the array
}
}
其他回答
看看Collections类,特别是shuffle(…)。
public class ShuffleArray {
public static void shuffleArray(int[] a) {
int n = a.length;
Random random = new Random();
random.nextInt();
for (int i = 0; i < n; i++) {
int change = i + random.nextInt(n - i);
swap(a, i, change);
}
}
private static void swap(int[] a, int i, int change) {
int helper = a[i];
a[i] = a[change];
a[change] = helper;
}
public static void main(String[] args) {
int[] a = new int[] { 1, 2, 3, 4, 5, 6, 6, 5, 4, 3, 2, 1 };
shuffleArray(a);
for (int i : a) {
System.out.println(i);
}
}
}
你应该使用Collections.shuffle()。但是,不能直接操作原始类型数组,因此需要创建包装器类。
试试这个。
public static void shuffle(int[] array) {
Collections.shuffle(new AbstractList<Integer>() {
@Override public Integer get(int index) { return array[index]; }
@Override public int size() { return array.length; }
@Override public Integer set(int index, Integer element) {
int result = array[index];
array[index] = element;
return result;
}
});
}
And
int[] solutionArray = {1, 2, 3, 4, 5, 6, 6, 5, 4, 3, 2, 1};
shuffle(solutionArray);
System.out.println(Arrays.toString(solutionArray));
输出:
[3, 3, 4, 1, 6, 2, 2, 1, 5, 6, 5, 4]
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;
}
}
}
Box from int[] to List<Integer> 用集合洗牌。洗牌法
int[] solutionArray = { 1, 2, 3, 4, 5, 6, 6, 5, 4, 3, 2, 1 };
List<Integer> list = Arrays.stream(solutionArray).boxed().collect(Collectors.toList());
Collections.shuffle(list);
System.out.println(list.toString());
// [1, 5, 5, 4, 2, 6, 1, 3, 3, 4, 2, 6]