leetcode15题给定一个包含 n 个整数的数组 nums，判断 nums 中是否存在三个元素 a，b，c ，使得 a + b + c = 0 ？找出所有满足条件且不重复的三元组。

桃扇骨 2022-05-19 19:54 58阅读 0赞

给定一个包含 *n* 个整数的数组 `nums`，判断 `nums` 中是否存在三个元素 *a，b，c ，*使得 *a + b + c = *0 ？找出所有满足条件且不重复的三元组。

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.

**注意：**答案中不可以包含重复的三元组。

**Note:**The solution set must not contain duplicate triplets.

public List<List<Integer>> threeSum(int[] nums) {
            Arrays.sort(nums);
            ArrayList<List<Integer>> result = new ArrayList<>();
            HashSet<List<Integer>> hashSet = new HashSet<>();
    
            for (int i = 0; i < nums.length - 2; i++) {
                if (nums[i] >  0) break;
    
                int low = i + 1;
                int high = nums.length - 1;
    
                while (low < high) {
                    if (nums[low] + nums[high] + nums[i] == 0) {
                        if (!hashSet.contains(Arrays.asList(nums[i], nums[low], nums[high]))) {
                            hashSet.add(Arrays.asList(nums[i], nums[low], nums[high]));
                            result.add(Arrays.asList(nums[i], nums[low], nums[high]));
                        }
    
                        while (low < high && nums[low] == nums[low + 1]) low++;
                        while (low < high && nums[high] == nums[high - 1]) high--;
    
                        low++;
                        high--;
                    } else if (nums[low] + nums[high] + nums[i] > 0 ) {
                        high--;
                    } else {
                        low++;
                    }
    
                }
            }
    
            return result;
        }