diff --git a/src/test/java/com/thealgorithms/misc/UniqueQuadruplets b/src/test/java/com/thealgorithms/misc/UniqueQuadruplets new file mode 100644 index 000000000000..2dec23689bc0 --- /dev/null +++ b/src/test/java/com/thealgorithms/misc/UniqueQuadruplets @@ -0,0 +1,50 @@ +package com.thealgorithms.misc; + +import java.util.ArrayList; +import java.util.Arrays; +import java.util.List; + +public class UniqueQuadruplets { + public static List> fourSum(int[] nums, int target) { + List> result = new ArrayList<>(); + if (nums == null || nums.length < 4) return result; + + Arrays.sort(nums); + + for (int i = 0; i < nums.length - 3; i++) { + // Skip duplicate values + if (i > 0 && nums[i] == nums[i - 1]) continue; + for (int j = i + 1; j < nums.length - 2; j++) { + // Skip duplicate values + if (j > i + 1 && nums[j] == nums[j - 1]) continue; + + 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])); + while (left < right && nums[left] == nums[left + 1]) left++; // Skip duplicates + while (left < right && nums[right] == nums[right - 1]) right--; // Skip duplicates + left++; + right--; + } else if (sum < target) { + left++; + } else { + right--; + } + } + } + } + return result; + } + + public static void main(String[] args) { + int[] arr1 = {1, 0, -1, 0, -2, 2}; + int target1 = 0; + System.out.println(fourSum(arr1, target1)); + + int[] arr2 = {4, 3, 3, 4, 4, 2, 1, 2, 1, 1}; + int target2 = 9; + System.out.println(fourSum(arr2, target2)); + } +}