3Sum(在一个数组中找到三个数字的和为0不重复)leetcode15

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]
]

code：

public List<List<Integer>> threeSum(int[] nums) {
        Arrays.sort(nums);
        List<List<Integer>> result=new ArrayList<>();
        for(int i=0;i<nums.length-2;){
            int target=-nums[i];
            int front=i+1;
            int last=nums.length-1;
            while(front<last){
                int sum=nums[front]+nums[last];
                if(sum<target)
                    front++;
                else if(sum>target)
                    last--;
                else{
                    List<Integer> list=new ArrayList<>();
                    list.add(-target);
                    list.add(nums[front]);
                    list.add(nums[last]);
                    result.add(list);
                    front++;
                    last--;
                    while(front<last&&nums[front-1]==nums[front]) 
                        front++;
                   while(last>front&&nums[last+1]==nums[last])
                        last--;
                }
            }
            i++;
            while (i  < nums.length && nums[i] == nums[i-1]) 
                i++;
        }
     
        return result;
    }