75 lines
1.3 KiB
Bash
75 lines
1.3 KiB
Bash
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#!/bin/bash
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declare -A mappings
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gcd() {
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local a=$1
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local b=$2
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while [ $b -ne 0 ]
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do
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local t=$b
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b=$(($a % $b))
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a=$t
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done
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echo ${a#-}
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}
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lcm() {
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local d=$(gcd $1 $2)
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echo $(($1 * $2 / $d))
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}
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findcount() {
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cur=$1
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instructions=$2
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pattern=$3
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count=0
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while [[ $cur != $pattern ]]
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do
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for (( idx = 0; idx < ${#instructions}; idx++ ))
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do
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((count += 1))
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instruction=${instructions:$idx:1}
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part=0
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if [ $instruction = "R" ]
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then
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part=4
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fi
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mapping=${mappings[$cur]}
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cur=${mapping:$part:3}
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if [[ $cur == $pattern ]]
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then
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break
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fi
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done
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done
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echo $count
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}
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# Parse inputs
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file="input.txt"
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instructions=$(head -n1 $file)
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while read line || [ -n "$line" ]
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do
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key=${line%% *}
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values=${line##*(}
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values=${values%)}
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mappings[$key]=${values/,/}
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done <<< $(tail -n +3 $file)
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# Part 1
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echo "Part 1: $(findcount "AAA" $instructions "ZZZ")"
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# Part 2
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count=1
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for key in ${!mappings[@]}
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do
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if [[ $key != *A ]]
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then
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continue
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fi
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cur=$key
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count=$(lcm $count $(findcount $cur $instructions "*Z"))
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done
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echo "Part 2: $count"
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