显示整数数组排列的Java程序

import java.util.Arrays;

public class ArrayPermutations {
    public static void main(String[] args) {
        int[] arr = {1, 2, 3};
        permute(arr, 0, arr.length - 1);
    }

    public static void permute(int[] arr, int startIndex, int endIndex) {
        if (startIndex == endIndex) {
            System.out.println(Arrays.toString(arr));
        } else {
            for (int i = startIndex; i <= endIndex; i++) {
                swap(arr, startIndex, i);
                permute(arr, startIndex + 1, endIndex);
                swap(arr, startIndex, i); // 回溯，还原数组
            }
        }
    }

    public static void swap(int[] arr, int i, int j) {
        int temp = arr[i];
        arr[i] = arr[j];
        arr[j] = temp;
    }
}

import java.util.ArrayList;
import java.util.List;

public class ArrayPermutationsIterative {
    public static void main(String[] args) {
        int[] arr = {1, 2, 3};
        List<List<Integer>> result = permute(arr);
        for (List<Integer> perm : result) {
            System.out.println(perm);
        }
    }

    public static List<List<Integer>> permute(int[] nums) {
        List<List<Integer>> result = new ArrayList<>();
        result.add(new ArrayList<>());

        for (int num : nums) {
            List<List<Integer>> current = new ArrayList<>();
            for (List<Integer> perm : result) {
                for (int i = 0; i <= perm.size(); i++) {
                    List<Integer> newPerm = new ArrayList<>(perm);
                    newPerm.add(i, num);
                    current.add(newPerm);
                }
            }
            result = current;
        }
        return result;
    }
}