Untitled

import java.util.*;

public class FourSum {
    public static List<List<Integer>> fourSum(int[] nums, int target) {
        List<List<Integer>> result = new ArrayList<>();
        Arrays.sort(nums); // Step 1: Sort the array
        
        for (int i = 0; i < nums.length - 3; i++) {
            if (i > 0 && nums[i] == nums[i - 1]) continue; // Skip duplicates for first number
            
            for (int j = i + 1; j < nums.length - 2; j++) {
                if (j > i + 1 && nums[j] == nums[j - 1]) continue; // Skip duplicates for second number
                
                int left = j + 1, right = nums.length - 1;
                while (left < right) {
                    int sum = nums[i] + nums[j] + nums[left] + nums[right];
                    
                    if (sum == target) {
                        result.add(Arrays.asList(nums[i], nums[j], nums[left], nums[right]));
                        left++;
                        right--;
                        
                        // Skip duplicates for left and right pointers
                        while (left < right && nums[left] == nums[left - 1]) left++;
                        while (left < right && nums[right] == nums[right + 1]) right--;
                    } else if (sum < target) {
                        left++; // Increase the sum
                    } else {
                        right--; // Decrease the sum
                    }
                }
            }
        }
        return result;
    }

    public static void main(String[] args) {
        int[] nums = {1, 0, -1, 0, -2, 2};
        int target = 0;
        System.out.println(fourSum(nums, target));
    }
}