고유 요소와 고유하지 않은 요소를 모두 처리하면서 배열의 가능한 모든 순열을 어떻게 생성할 수 있습니까?

// Recursive method for permutation generation
public static void permute(int[] arr, int k) {
    for (int i = k; i < arr.length; i++) {
        // Swap elements at positions k and i
        Collections.swap(arr, k, i);
        // Recursively permute the remaining elements
        permute(arr, k + 1);
        // Restore original order of elements
        Collections.swap(arr, k, i);
    }
    if (k == arr.length - 1) {
        // Once all elements are permuted, print the current permutation
        System.out.println(Arrays.toString(arr));
    }
}

for (int tail = arr.length - 1; tail > 0; tail--) {
    // Find the first decreasing element from the end
    if (arr[tail - 1] < arr[tail]) {
        // Find the last element greater than the decreasing element
        int s = arr.length - 1;
        while (arr[tail - 1] >= arr[s]) {
            s--;
        }
        // Swap the decreasing element with the greater element
        swap(arr, tail - 1, s);
        // Reverse the order of elements after the swap
        reverse(arr, tail);
        break;
    }
}

// Create a HashMap to map elements to their indices
Map<E, Integer> map = new HashMap<>();
for (int i = 0; i < arr.length; i++) {
    map.put(arr[i], i);
}
// Sort the array in ascending order
Arrays.sort(arr);
// Initialize the index array
int[] ind = new int[arr.length];
for (int i = 0; i < arr.length; i++) {
    ind[i] = map.get(arr[i]);
}