二、解题思路

1.回溯+DFS。

2.注意当所加数之和大于target则返回，等于target则记录。

三、代码

[code]import copy

class Solution:
def combinationSum(self, candidates: list, target: int) -> list:
n = len(candidates)
ans = []
res = []
def dfs(index, n, su, ans):
if su == target:
if res not in ans:
ans.append(res.copy())
# print(ans)
if su > target:
return
for i in range(index, n):
su += candidates[i]
res.append(candidates[i])
dfs(i, n, su, ans)
su -= candidates[i]
res.remove(candidates[i])
dfs(0, n, 0, ans)
return ans

if __name__ == '__main__':
candidates = [2, 3, 6, 7]
target = 7
s = Solution()
ans = s.combinationSum(candidates, target)
print(ans)