Combination Sum III

Problem: Combination Sum III

Solution of this problem is quite similar to Combination Sum so I won't explain any more.

Code in Python:

class Solution(object):
    def combinationSum3(self, k, n):
        """
        :type k: int
        :type n: int
        :rtype: List[List[int]]
        """
        nums = [1, 2, 3, 4, 5, 6, 7, 8, 9]
        ans = []
        def helper(pos, sum, current):
            if len(current) < k:
                for i in xrange(pos, len(nums)):
                    if sum + nums[i] == n and len(current) == k-1: ans.append(current+[nums[i]])
                    elif sum + nums[i] < n - nums[i]: helper(i+1, sum+nums[i], current+[nums[i]])
        helper(0, 0, [])
        return ans