LeetCode---216. Combination Sum III

题目

给出n和k，从1到9中选出k个数，使得k个数的和为n。1到9每个数只能使用1次。

Python题解

class Solution(object):
    def combinationSum3(self, k, n):
        """
        :type k: int
        :type n: int
        :rtype: List[List[int]]
        """
        path, res = [], []
        self.dfs(k, n, 1, path, res)
        return res

    def dfs(self, k, n, index, path ,res):
        if k == 0:
            if sum(path) == n:
                res.append(path[:])
        else:
            for i in range(index, 10):
                path.append(i)
                self.dfs(k - 1, n, i + 1, path, res)
                path.pop(-1)