递归和回溯_leetcode216

class Solution(object):
    def combinationSum3(self, k, n):
        """
        :type k: int
        :type n: int
        :rtype: List[List[int]]
        """

        self.res = []

        self.generateCombination(k,n,1,[])

        print self.res
        return self.res


    def generateCombination(self,k,n,start,ans):
        pass

        if len(ans) == k:

            if sum(ans) == n:
                self.res.append(ans[0:])
            else:
                return


        for i in range(start,10):

            ans.append(i)
            self.generateCombination(k,n,i+1,ans)
            ans.pop()




s = Solution()

k = 3
n = 7

s.combinationSum3(3,9)