classSolution{ public List<List<Integer>> threeSum(int[] num) { Arrays.sort(num); List<List<Integer>> res = new LinkedList<>(); for (int i = 0; i < num.length - 2; i++) { if (i == 0 || (i > 0 && num[i] != num[i - 1])) { int lo = i + 1, hi = num.length - 1, sum = 0 - num[i]; while (lo < hi) { if (num[lo] + num[hi] == sum) { res.add(Arrays.asList(num[i], num[lo], num[hi])); while (lo < hi && num[lo] == num[lo + 1]) lo++; while (lo < hi && num[hi] == num[hi - 1]) hi--; lo++; hi--; } elseif (num[lo] + num[hi] < sum) lo++; else hi--; } } } return res; } }