2021 AOC in sed

day_1.sed

#!/bin/sed -Enf

# Note: this code is intended for GNU sed, other implementations of sed might have issues running it.
#
# Usage:
# $ ./day_1.sed < ./input.txt

G
s/\n/;/m
h

s/[0-9]/u/g

G
s/\n/#/m
s/;[^;]*$/;/

s/^(u+)u+;\1;.*/&a/
s/^(u+);\1;.*#(\w*)(\w)\w*;\2(\w).*/&a\3\4/
s/^(u+)u+;u+;u+;\1;.*/&b/
s/^(u+);u+;u+;\1;.*#(\w*)(\w)\w*;\w+;\w+;\2(\w).*/&b\3\4/

s/[ab](99|8[89]|7[7-9]|6[6-9]|5[5-9]|4[4-9]|3[3-9]|2[2-9]|1[^0]|0.)//g
s/[^ab]//g

G
s/^(a?)(b?)\n(\w*;\w*;?\w*;?)[^#]*(#(\w*) (\w*)|$)/\3#\5\1 \6\2/m
s/b/a/

:a
s/9a/a0/g
ta

s/(#| )a/\11/g
s/8a/9/g
s/7a/8/g
s/6a/7/g
s/5a/6/g
s/4a/5/g
s/3a/4/g
s/2a/3/g
s/1a/2/g
s/0a/1/g

h

$s/[^#]*#//p