在Java中迭代地生成所有的字符串置换对

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

public class StringPermutation {
    public static List<String[]> generatePermutations(String str) {
        List<String[]> permutations = new ArrayList<>();
        generatePermutationsHelper(str.toCharArray(), 0, permutations);
        return permutations;
    }

    private static void generatePermutationsHelper(char[] strArray, int index, List<String[]> permutations) {
        if (index == strArray.length - 1) {
            String[] permutation = new String[2];
            permutation[0] = new String(strArray);
            permutation[1] = new String(strArray);
            permutations.add(permutation);
        } else {
            for (int i = index; i < strArray.length; i++) {
                swap(strArray, index, i);
                generatePermutationsHelper(strArray, index + 1, permutations);
                swap(strArray, index, i); // backtrack
            }
        }
    }

    private static void swap(char[] strArray, int i, int j) {
        char temp = strArray[i];
        strArray[i] = strArray[j];
        strArray[j] = temp;
    }

    public static void main(String[] args) {
        String str = "abc";
        List<String[]> permutations = generatePermutations(str);
        for (String[] permutation : permutations) {
            System.out.println(permutation[0] + " " + permutation[1]);
        }
    }
}