Algorithm Interview: Smallest Number that is not a Sum of a Subset of List

Hi, here's your problem today. This problem was recently asked by AirBNB:

Given a sorted list of positive numbers, find the smallest positive number that cannot be a sum of any subset in the list.

Example:
Input: [1, 2, 3, 8, 9, 10]
Output: 7
Numbers 1 to 6 can all be summed by a subset of the list of numbers, but 7 cannot.

def findSmallest(nums):

  # Fill this in.



print findSmallest([1, 2, 3, 8, 9, 10])

# 7