Solution2.py

class Solution:
    def combinationSum2(self, candidates: List[int], target: int) -> List[List[int]]:
        def dfs(i: int, s: int):
            if s == 0:
                ans.append(t[:])
                return
            if i >= len(candidates) or s < candidates[i]:
                return
            x = candidates[i]
            t.append(x)
            dfs(i + 1, s - x)
            t.pop()
            while i < len(candidates) and candidates[i] == x:
                i += 1
            dfs(i, s)

        candidates.sort()
        ans = []
        t = []
        dfs(0, target)
        return ans