import java.util.*;

public class Solution {

public List<List<Integer>> threeSum(int[] num) {

Arrays.sort(num);

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

int n = num.length;

for (int i = 0; i < n - 2; i++) {

if (i > 0 && num[i] == num[i - 1]) continue;

int low = i + 1;

int high = n - 1;

while (low < high) {

int sum = num[i] + num[low] + num[high];

if (sum > 0) {

while (high > 0 && num[high] == num[high - 1]) high--;

high--;

} else if (sum < 0) {

while (low < n - 1 && num[low] == num[low + 1]) low++;

low++;

} else {

ret.add(Arrays.asList(num[i], num[low], num[high]));

while (high > 0 && num[high] == num[high - 1]) high--;

high--;

while (low < n - 1 && num[low] == num[low + 1]) low++;

low++;

}

}

}

return ret;

}

public static void main(String[] args) {

Solution s = new Solution();

int[] arr;

arr = new int[] { -1, 0, 1, 2, -1, -4};

for (List<Integer> a : s.threeSum(arr)) {

System.out.println(a);

}

arr = new int[] { 0, 0, 0, 0};

for (List<Integer> a : s.threeSum(arr)) {

System.out.println(a);

}

}

}