# Factor Combinations

Numbers can be regarded as product of its factors. For example,

```
8 = 2 x 2 x 2;
  = 2 x 4.
```

Write a function that takes an integernand return all possible combinations of its factors.

**Note:**

1. You may assume that n is always positive.
2. Factors should be greater than 1 and less than n.

## Example

**Example 1:**

```
Input: 1
Output: []
```

**Example 2:**

```
Input: 37
Output: []
```

**Example 3:**

```
Input: 12
Output:
[
  [2, 6],
  [2, 2, 3],
  [3, 4]
]
```

**Example 4:**

```
Input: 32
Output:
[
  [2, 16],
  [2, 2, 8],
  [2, 2, 2, 4],
  [2, 2, 2, 2, 2],
  [2, 4, 4],
  [4, 8]
]
```

## Note

DFS去寻找

## Code

```java
public List<List<Integer>> getFactors(int n) {
    List<List<Integer>> result = new ArrayList<List<Integer>>();
    helper(result, new ArrayList<Integer>(), n, 2);
    return result;
}

public void helper(List<List<Integer>> result, List<Integer> item, int n, int start){
    if (n <= 1) {
        if (item.size() > 1) {
            result.add(new ArrayList<Integer>(item));
        }
        return;
    }

    for (int i = start; i <= n; ++i) {
        if (n % i == 0) {
            item.add(i);
            helper(result, item, n/i, i);
            item.remove(item.size()-1);
        }
    }
}
```

```python
class Solution:
    def getFactors(self, n: 'int') -> 'List[List[int]]':
        def dfs(res, path, start, n):
            while start*start <= n:
                if n % start == 0:
                    res.append(path + [start, n//start])
                    dfs(res, path + [start], start, n//start)
                start += 1
        res = []
        dfs(res, [], 2, n)
        return res
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://luj.gitbook.io/code/dfs/enumeration/factor-combinations.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.