C 2022/Day 3 final ľeanup and comments

2022/day04/aoc.bash

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+#!/usr/bin/env bash
+#
+# aoc.bash: Advent of Code 2022, day 3
+#
+# Copyright (C) 2022 Bruno Raoult ("br")
+# Licensed under the GNU General Public License v3.0 or later.
+# Some rights reserved. See COPYING.
+#
+# You should have received a copy of the GNU General Public License along with this
+# program. If not, see <https://www.gnu.org/licenses/gpl-3.0-standalone.html>.
+#
+# SPDX-License-Identifier: GPL-3.0-or-later <https://spdx.org/licenses/GPL-3.0-or-later.html>
+
+. common.bash
+
+export LANG=C
+declare -a input
+
+# prio - get priority value for an item
+# $1: reference of variable for result
+# $2: string
+prio() {
+    local -n _val="$1"
+    local _char="${2:0:1}"
+
+    printf -v _val "%d" "'$_char"
+    if [[ $_char > "Z" ]]; then                   # a-z
+        ((_val += (1 - 97) ))
+    else                                          # A-Z
+        ((_val += (27 - 65) ))
+    fi
+}
+
+# common=chars - get common characters in two strings
+# $1: reference of variable for result
+# $2, $3: The two strings
+common_chars() {
+    local -n _res="$1"
+
+    _res="${2//[^$3]}"
+}
+
+parse() {
+    readarray -t input
+}
+
+part1() {
+    local line half1 half2 common
+    local -i half i prio
+    declare -ig res=0
+
+    for line in "${input[@]}"; do
+        (( half = ${#line} / 2 ))
+        half1="${line:0:half}"
+        half2="${line:half}"
+        common="${half1//[^${half2}]}"
+        prio prio "${common}"
+        (( res += prio ))
+    done
+}
+
+part2() {
+    local one two three common
+    local -i i prio
+    declare -ig res=0
+
+    for (( i = ${#input[@]} - 1; i > 1; i -= 3)); do
+        three=${input[i]}
+        two=${input[i - 1]}
+        one=${input[i - 2]}
+        common_chars common "$three" "$two"
+        common_chars common "$common" "$one"
+        prio prio "${common}"
+        (( res += prio ))
+    done
+}
+
+solve() {
+    if (($1 == 1)); then
+        part1
+    else
+        part2
+    fi
+}
+
+main "$@"
+exit 0