class Solution {
public List<List<Integer>> threeSum(int[] nums) {
List<List<Integer>> res = new ArrayList<>();
int n = nums.length;
if(n <= 2) return res;
Arrays.sort(nums);
for(int i=0; i < n-2; i++) {
if(i > 0 && nums[i] == nums[i-1]) continue;
int target = -nums[i],l = i+1, r = n-1;
while(l < r) {
int temp = nums[l] + nums[r];
if(temp > target) r--;
else if(temp < target) l++;
else {
res.add(Arrays.asList(nums[i], nums[l], nums[r]));
while(l+1 < r && nums[l] == nums[l+1]) l++;
while(l < r-1 && nums[r] == nums[r-1]) r--;
l ++; r--;
}
}
}
return res;
}
}