126 lines
3.5 KiB
Bash
126 lines
3.5 KiB
Bash
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#!/usr/bin/env bash
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set -o errexit
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set -o nounset
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set -o pipefail
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if [[ "${TRACE-0}" == "1" ]]; then
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set -o xtrace
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fi
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LINES=$(wc -l < "$1")
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COLUMNS=140
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mapfile -t -O 1 INPUT < "$1"
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declare -a gear_ratios
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find_gears ()
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{
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# Find and append gear ratios to array.
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for ((line=1; line<=LINES; line++)); do
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for ((column=1; column<=COLUMNS; column++)); do
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if [[ $(arr "${line}" "${column}") =~ ^\*$ ]]; then
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declare -i ratio=1
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declare -a adjacent=()
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for ((i=column-1; i<=column+1; i++)); do # check above
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if [[ $(arr $((line-1)) "${i}") =~ ^[0-9]$ ]]; then
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number="$(arr $((line-1)) "${i}")"
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for ((j=i-1; j>i-3; j--)); do # check before i, numbers are max 3-digit
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if [[ $(arr $((line-1)) "${j}") =~ ^[0-9]$ ]]; then
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number="$(arr $((line-1)) "${j}")${number}"
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else
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break
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fi
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done
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add_to_i=0
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for ((k=i+1; k<i+3; k++)); do # check after i
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if [[ $(arr $((line-1)) "${k}") =~ ^[0-9]$ ]]; then
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number="${number}$(arr $((line-1)) "${k}")"
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add_to_i=$((add_to_i+1))
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else
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break
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fi
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done
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i=$((i+add_to_i))
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adjacent+=("${number}")
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fi
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done
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for ((i=column-1; i<=column+1; i++)); do # check below
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if [[ $(arr $((line+1)) "${i}") =~ ^[0-9]$ ]]; then
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number="$(arr $((line+1)) "${i}")"
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for ((j=i-1; j>i-3; j--)); do # check before i
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if [[ $(arr $((line+1)) "${j}") =~ ^[0-9]$ ]]; then
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number="$(arr $((line+1)) "${j}")${number}"
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else
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break
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fi
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done
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add_to_i=0
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for ((k=i+1; k<i+3; k++)); do # check after i
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if [[ $(arr $((line+1)) "${k}") =~ ^[0-9]$ ]]; then
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number="${number}$(arr $((line+1)) "${k}")"
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add_to_i=$((add_to_i+1))
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else
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break
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fi
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done
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i=$((i+add_to_i))
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adjacent+=("${number}")
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fi
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done
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if [[ $(arr "${line}" $((column-1))) =~ ^[0-9]$ ]]; then # check before gear
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number="$(arr "${line}" $((column-1)))"
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for ((i=column-2; i>column-4; i--)); do # search for beginning
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if [[ $(arr "${line}" "${i}") =~ ^[0-9]$ ]]; then
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number="$(arr "${line}" "${i}")${number}"
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else
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break
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fi
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done
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adjacent+=("${number}")
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fi
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if [[ $(arr "${line}" $((column+1))) =~ ^[0-9]$ ]]; then # check after gear
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number="$(arr "${line}" $((column+1)))"
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for ((i=column+2; i<column+4; i++)); do # search for end
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if [[ $(arr "${line}" "${i}") =~ ^[0-9]$ ]]; then
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number="${number}$(arr "${line}" "${i}")"
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else
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break
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fi
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done
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adjacent+=("${number}")
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fi
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if [[ ${#adjacent[@]} -gt 1 ]]; then
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for number in "${adjacent[@]}"; do
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ratio=$((ratio*number))
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done
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gear_ratios+=("${ratio}")
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fi
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fi
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done
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done
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}
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arr ()
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{
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# Usage: arr LINE COLUMN
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line="$1"
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column=$(($2-1))
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if ((line<=0)) || ((line>LINES)) || ((column<0)); then
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echo -n ''
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else
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echo -n "${INPUT[${line}]:${column}:1}"
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fi
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}
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main ()
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{
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find_gears
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sum=0
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for number in "${gear_ratios[@]}"; do
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sum=$((sum+number))
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done
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echo "${sum}"
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}
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main
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