Advent of Code 2023 Day 1

Author

Nathan Moore

— Day 1: Trebuchet?! —

The calibration document for the trebuchet sending you into the sky isn’t quite right. Combine the first and last digits from each line to find the calibration value.

What is the sum of all of the calibration values?

with open('data-2023-01.txt', 'r') as f:
    inp = f.read().splitlines()

Find the first and last digit in a string. We could use re or split the string with list comprehension.

# let's try regex first
import re

get_digi = [re.findall(r'\d', x) for x in inp]

double_digi = [int(x[0])*10 + int(x[-1]) for x in get_digi]

sum(double_digi)

This could work with splitting a string forwards and backwards, and is more like what I think part 2 will be which is including the numbers as words.

first_digi = []
last_digi = []

for i in inp:
    # forwards
    for s in str(i): 
        if s.isdigit(): 
            first_digi.append(int(s))
            break
    # reverse the string
    for s in i[::-1]:
        if s.isdigit():
            last_digi.append(int(s))
            break

double_digi_1 = [f*10+l for f,l in zip(first_digi, last_digi)]

sum(double_digi_1)

Part one: 54916

Part Two

Oops, there are “digits” that are actually spelled out.

What is the sum of all of the calibration values?

I think I want to make a function first to return the digit found, that’ll be much nicer in the long run for the loop of input.

def get_first(ss):
    """Get the first digit, numeric or spelled, from the input string ss"""
    # define dict for values
    nums = {'one': 1, 
            'two': 2, 
            'three': 3, 
            'four': 4, 
            'five': 5, 
            'six': 6, 
            'seven': 7, 
            'eight': 8, 
            'nine': 9,
            }

    # loop through the input
    for s in range(len(ss)): 
        # simplest case first, we've found an actual digit
        if ss[s].isdigit(): 
            return int(ss[s])
        for k,v in nums.items(): 
            if ss[s:s+len(k)] == k:
                return v
 
def get_last(ss):
    """
    Get the LAST digit, numeric or spelled, from the input string ss
    The input string is already reversed, so we need to reverse our numbers
    """
    # define dict for values
    nums = {'eno': 1, 
            'owt': 2, 
            'eerht': 3, 
            'ruof': 4, 
            'evif': 5, 
            'xis': 6, 
            'neves': 7, 
            'thgie': 8, 
            'enin': 9,
            }

    # loop through the input
    for s in range(len(ss)): 
        # simplest case first, we've found an actual digit
        if ss[s].isdigit(): 
            return int(ss[s])
        for k,v in nums.items(): 
            if ss[s:s+len(k)] == k:
                return v

Now do the searching and gathering

first_digi = []
last_digi = []

for i in inp:
    first_digi.append(get_first(i))
    last_digi.append(get_last(i[::-1]))

double_digi_2 = [f*10+l for f,l in zip(first_digi, last_digi)]

sum(double_digi_2)

Part two: 54728