3Sum
Given an array nums of n integers, are there elements a , b , c in nums such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero. Note: The solution set must not contain duplicate triplets. Example: Given array nums = [-1, 0, 1, 2, -1, -4], A solution set is: [ [-1, 0, 1], [-1, -1, 2] ] class Solution { public List<List<Integer>> threeSum(int[] nums) { if (nums.length < 3) return new ArrayList<>(); Arrays.sort(nums); Set<List<Integer>> triplet= new HashSet<>(); for (int i = 0; i < nums.length - 2; i++) { int j = i + 1; int k = nums.length - 1; while (j < k) { int sum = nums[i] + nums[j] + nums[k]; if (sum == 0) triplet.add(Arrays.asList(nums[i], nums[j++], nums[k--])); else if (sum > 0) k--; else if (sum < 0) j++; }