Sorted two pointer two sum with a outter loopThe key is to avoid duplicates, in the outer loop when num[i] == num[i - 1], continue, so you only use the first element of duplicated element. In the inner loop also, i and j need to avoid duplicates using a while loop for (int i = 0; i < n; i++) { if (i != 0 && numbers[i] == numbers[i - 1]) { continue; } int j = i + 1, k = n - 1; while (j < k) { if (numbers[j] + numbers[k] > -numbers[i]) { int number = numbers[k]; while (k > j && numbers[k] == number) { k--; } } else if (numbers[j] + numbers[k] < -numbers[i]) { int number = numbers[j]; while (j < k && numbers[j] == number) { j++; } } else { ArrayList<Integer> tmp = new ArrayList<Integer>(Arrays.asList(numbers[i], numbers[j], numbers[k])); Collections.sort(tmp); res.add(tmp); int number = numbers[k]; while (k > j && numbers[k] == number) { k--; } number = numbers[j]; while (j < k && numbers[j] == number) { j++; } } }

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