Untitled

import java.util.*;

class Solution {
    public List<List<Integer>> permuteUnique(int[] nums) {
        List<List<Integer>> result = new ArrayList<>();
        // First sort the array to handle duplicates effectively
        Arrays.sort(nums);
        boolean[] used = new boolean[nums.length];
        backtrack(nums, used, new ArrayList<>(), result);
        return result;
    }
    
    private void backtrack(int[] nums, boolean[] used, List<Integer> current, List<List<Integer>> result) {
        // When current permutation is complete, add it to result
        if (current.size() == nums.length) {
            result.add(new ArrayList<>(current));
            return;
        }
        
        // Try each number as the next element in the permutation
        for (int i = 0; i < nums.length; i++) {
            // Skip if the number is already used in current permutation
            if (used[i]) continue;
            
            // Skip duplicates to avoid generating same permutations
            // We only want to use same number again if its previous occurrence was used
            if (i > 0 && nums[i] == nums[i-1] && !used[i-1]) continue;
            
            // Include current number in permutation
            used[i] = true;
            current.add(nums[i]);
            
            // Recursively generate remaining permutation
            backtrack(nums, used, current, result);
            
            // Backtrack: remove current number to try next possibility
            used[i] = false;
            current.remove(current.size() - 1);
        }
    }
    
    public static void main(String[] args) {
        Solution solution = new Solution();
        
        // Test cases
        int[] nums1 = {1, 1, 2};
        System.out.println("Input: [1,1,2]");
        System.out.println("Output: " + solution.permuteUnique(nums1));
        // Expected output: [[1,1,2], [1,2,1], [2,1,1]]
        
        int[] nums2 = {1, 2, 2};
        System.out.println("\nInput: [1,2,2]");
        System.out.println("Output: " + solution.permuteUnique(nums2));
        // Expected output: [[1,2,2], [2,1,2], [2,2,1]]
    }
}