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 2 3 4
[ [-1, 0, 1], [-1, -1, 2] ]
Code
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public List<List<Integer>> threeSum(int [] nums) { List<List<Integer>> result = new ArrayList<>(); Arrays.sort(nums); for (int i = 0 ; i < nums.length - 2 ; i++) { if (i > 0 && nums[i] == nums[i - 1 ]) continue ; twoSum(nums, -nums[i], i + 1 , nums.length - 1 , result); } return result; } private void (int [] nums, int target, int left, int right, List<List<Integer>> result) { while (left < right) { if (nums[left] + nums[right] == target) { result.add(Arrays.asList(-target, nums[left], nums[right])); left++; right--; while (left < right && nums[left] == nums[left - 1 ]) left++; while (left < right && nums[right] == nums[right + 1 ]) right--; } else if (nums[left] + nums[right] < target) left++; else right--; } }
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