[LC] 39. Combination Sum

Given a set of candidate numbers (candidates) (without duplicates) and a target number (target), find all unique combinations in candidates where the candidate numbers sums to target.

The same repeated number may be chosen from candidates unlimited number of times.

Note:

• All numbers (including target) will be positive integers.
• The solution set must not contain duplicate combinations.

Example 1:

Input: candidates = [2,3,6,7], target = 7,
A solution set is:
[
  [7],
  [2,2,3]
]

Example 2:

Input: candidates = [2,3,5], target = 8,
A solution set is:
[
  [2,2,2,2],
  [2,3,3],
  [3,5]
]

Time: O(N^|target|)
Space: O(|target|)

 1 class Solution:
 2     def combinationSum(self, candidates: List[int], target: int) -> List[List[int]]:
 3         res = []
 4         lst = []
 5         self.dfs(candidates, lst, res, 0, target)
 6         return res
 7     
 8     def dfs(self, candidates, lst, res, start, reminder):
 9         if reminder < 0:
10             return
11         if reminder == 0:
12             res.append(list(lst))
13             return
14         for i in range(start, len(candidates)):
15             cur_num = candidates[i]
16             lst.append(cur_num)
17             self.dfs(candidates, lst, res, i, reminder - cur_num)
18             lst.pop()
19 
20