I’m a little confused about problem 13. I wanted to come up with some nice way to find the first (leftmost) 10 digits of the sum. The only way I came up with was to actually do the sum though. I thought maybe that coding this up would point out something I hadn’t thought about that made the problem more difficult. Like maybe the 50 digit numbers were too big to store as integer values, or the sum was, or something. So I just coded up the naive solution to see what would happen:

from __future__ import with_statement
import sys, time
def readin(filename):
""" Input a file, reading into a list of integers """
ret = []
with open(filename) as file:
for line in file:
ret.append(int(line))
return ret
def solve(nums):
""" The leading 10 digits of the sum of the numbers in the list nums """
return str(sum(nums))[0:10] # loving this syntax
if __name__ == "__main__":
t = time.time()
ans = solve(readin(sys.argv[1]))
t = time.time() - t
print solve(readin(sys.argv[1])), t

I ran that, and it spit out an answer in about 0.0004 seconds.

So, am I missing something from this exercise, or is it that easy? Is there a more clever way to do it anyway?

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Tags: nah, prob13, python

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