Advent-Of-Code-2024/day/02/part2.sh
2024-12-19 17:54:18 +00:00

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#! /bin/bash
#set -x
FILE_IN="${1}"
safe_count=0
function debug_echo() {
echo "$@" 1>&2
}
function check_is_safe() {
local is_up_down="${1}"
local first_val="${2}"
local second_val="${3}"
local fun_is_safe=1
prev_diff=$((first_val - second_val))
debug_echo "diff ${prev_diff}"
if [[ "${prev_diff}" -gt 0 ]]; then
debug_echo "going up"
if [[ "${is_up_down}" -le 0 ]]; then
debug_echo "wrong direction"
fun_is_safe=0
fi
else
debug_echo "going down"
if [[ "${is_up_down}" -ge 0 ]]; then
debug_echo "wrong direction"
fun_is_safe=0
fi
fi
if [[ "${prev_diff#-}" -le 0 ]] || [[ "${prev_diff#-}" -ge 4 ]]; then
debug_echo "outside range"
fun_is_safe=0
fi
if [[ "${fun_is_safe}" -ne 0 ]]; then
debug_echo "safe"
else
debug_echo "unsafe"
fi
echo "${fun_is_safe}"
}
while read -r l; do
echo "reading new line [$l]"
IFS=" "
read -ra line_split <<< "${l}"
unset IFS
# start with the first val
prev_val="${line_split[0]}"
is_safe=2
# if positive, going up, if negative, going down!
is_up_down="$((line_split[1] - line_split[0]))"
safety_trigger=1
if [[ "${is_up_down}" -ge 0 ]]; then
echo "Initially going up"
else
echo "Initially going down"
fi
for idx in "${!line_split[@]}"; do
[[ "${idx}" -eq 0 ]] && continue
echo "index $idx"
v="${line_split[${idx}]}"
echo "checking [${v}] against previous [${prev_val}]"
test_is_safe=$(check_is_safe "${is_up_down}" "${v}" "${prev_val}")
debug_echo "safe val ${test_is_safe}"
if [[ "${test_is_safe}" -eq 0 ]]; then
# normally we fail this set
is_safe=$((is_safe - 1))
fi
if [[ "${test_is_safe}" -eq 0 ]] && [[ "${safety_trigger}" -eq 1 ]]; then
# but we let 1 happen if the trigger hasnt... triggered
safety_trigger=0
if [[ "${idx}" -eq 1 ]]; then
# we may have to re-calculate is_up_down!
is_up_down="$((line_split[2] - line_split[0]))"
echo "allowing flip up/down"
fi
echo "-------------------"
echo "allowing 1 failure!"
echo "-------------------"
else
# we skip the re-assign once to 'skip' a number
prev_val=$v
fi
done
if [[ "${is_safe}" -gt 0 ]]; then
safe_count=$((safe_count + 1))
fi
done <"$FILE_IN"
echo "final safe count ${safe_count}"