Medium
我一刷的时候写的是"似懂非懂”， 然后二刷的时候就没做出来。彻底理解一道题比刷完重要很多，刷题一定要重视质量。我是因为最近要面试了狂刷tag题过得比较快，但重点题还是得扣细节.
class Solution {
public List<List<Integer>> getFactors(int n) {
List<List<Integer>> res = new ArrayList<>();
List<Integer> list = new ArrayList<>();
dfsHelper(res, list, 2, 1, n);
return res;
}
private void dfsHelper(List<List<Integer>> res, List<Integer> list, int startNum, int product, int n){
if (startNum > n || product > n){
return;
}
if (product == n){
//Q? when to use Arrays.asList()
res.add(new ArrayList<>(list));
return;
}
for (int i = startNum; i < n; i++){
if (i*product > n){
break;
}
if (n % i == 0){
list.add(i);
dfsHelper(res, list, i, product * i, n);
list.remove(list.size() - 1);
}
}
}
}
