Leetcode(java) 15. 3Sum

Q:

Given an integer array nums, return all the triplets [nums[i], nums[j], nums[k]] such that i != j, i != k, and j != k, and nums[i] + nums[j] + nums[k] == 0.

Notice that the solution set must not contain duplicate triplets.

A: Firstly , choose one element, then use two pointers to scan the array and judge whether theses three elements satisfy the requirement.

class Solution {
    public List<List<Integer>> threeSum(int[] nums) {
            Arrays.sort(nums);

           List<List<Integer>> res = new ArrayList<List<Integer>>();

            for(int i=0;i<nums.length-2;i++){
                if(nums[i]>0) break;
                if(i==0 || nums[i]>nums[i-1]){
                    int target = -nums[i];
                    int left = i+1;
                    int right = nums.length-1;
                    while(left<right){
                        if((nums[left]+nums[right])==target){
                          
                            res.add(Arrays.asList(nums[i],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--;
                        }
                        
                    }

                }
                
            }
            return res;
    }
}