class Solution:
def combinationSum(self, candidates: List[int], target: int) -> List[List[int]]:
if(not candidates):
return []
n=len(candidates)
res=[]
candidates.sort()
def helper(i,tmp,target):
if(target==0):
res.append(tmp)
return
if(i==n or target<candidates[i]):
return
helper(i,tmp+[candidates[i]],target-candidates[i])
helper(i+1,tmp,target)
helper(0,[],target)
return res