Numbers can be regarded as product of its factors. For example,
1 2
| 8 = 2 x 2 x 2; = 2 x 4.
|
Write a function that takes an integer n and return all possible combinations of its factors.
Note:
Each combination’s factors must be sorted ascending, for example: The factors of 2 and 6 is [2, 6]
, not [6, 2]
.
You may assume that n is always positive.
Factors should be greater than 1
and less than n
.
Examples:
input: 1
output:
input: 37
output:
input: 12
output:
1 2 3 4 5
| [ [2, 6], [2, 2, 3], [3, 4] ]
|
input: 32
output:
1 2 3 4 5 6 7 8
| [ [2, 16], [2, 2, 8], [2, 2, 2, 4], [2, 2, 2, 2, 2], [2, 4, 4], [4, 8] ]
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40
| public class Solution { public List<List<Integer>> getFactors(int n) { Set<List<Integer>> result = new HashSet<>();
int dist = (int) Math.sqrt(n);
for (int i = 2; i <= dist; i++) { if (n % i == 0) { List<List<Integer>> tmp = helper(n / i); for (List<Integer> l : tmp) { l.add(i); Collections.sort(l); result.add(l); } } } return new ArrayList<>(result); }
public List<List<Integer>> helper(int n) { List<List<Integer>> result = new ArrayList<>();
List<Integer> t = new ArrayList<>(); t.add(n); result.add(t);
int dist = (int) Math.sqrt(n);
for (int i = 2; i <= dist; i++) { if (n % i == 0) { List<List<Integer>> tmp = helper(n / i); for (List<Integer> l : tmp) { l.add(i); result.add(l); } } } return result; } }
|