Created
January 2, 2024 15:05
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Advent of Code - day 9
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<?php | |
declare(strict_types=1); | |
//$input = file('sample.txt', FILE_IGNORE_NEW_LINES); | |
$input = file('input.txt', FILE_IGNORE_NEW_LINES); | |
$totalNextNumbers = 0; | |
$totalPreviousNumbers = 0; | |
foreach ($input as $line) { | |
$numbers = explode(' ', $line); | |
[$nextNumber, $previousNumber] = findNextAndPreviousNumber($numbers); | |
printf('Next line in number sequence "%s" is: %s' . PHP_EOL, $line, $nextNumber); | |
printf('...and the previous number is: %s' . PHP_EOL, $previousNumber); | |
$totalNextNumbers += $nextNumber; | |
$totalPreviousNumbers += $previousNumber; | |
} | |
printf('Total difference for next numbers: %s' . PHP_EOL, $totalNextNumbers); | |
printf('Total different for previous numbers: %s' . PHP_EOL, $totalPreviousNumbers); | |
function findNextAndPreviousNumber(array $numbers): array | |
{ | |
$numbersList = []; | |
while (areAllSameNumbers($numbers) === false) { | |
$numbersList[] = $numbers; | |
$numbers = findDifferences($numbers); | |
} | |
$nextNumber = $numbers[0]; | |
$previousNumber = $numbers[0]; | |
foreach (array_reverse($numbersList) as $list) { | |
$nextNumber = end($list) + $nextNumber; | |
$previousNumber = reset($list) - $previousNumber; | |
} | |
return [$nextNumber, $previousNumber]; | |
} | |
function findDifferences(array $numbers): array | |
{ | |
$newNumbers = []; | |
for ($i = 1; $i < count($numbers); $i++) { | |
$newNumbers[] = $numbers[$i] - $numbers[$i - 1]; | |
} | |
return $newNumbers; | |
} | |
function areAllSameNumbers(array $numbers): bool | |
{ | |
return implode('', $numbers) === str_repeat((string)$numbers[0], count($numbers)); | |
} | |
function dd($a, $b = null, $c = null, $d = null): void | |
{ | |
die(var_dump($a, $b, $c, $d)); | |
} |
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