63 lines
1.3 KiB
PHP
63 lines
1.3 KiB
PHP
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<?php
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[$min, $max] = explode('-', file_get_contents('input.txt'));
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/**
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* @param int|string $big_number
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*
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* @return bool
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*/
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function has_no_more_than_two_adjacent_number($big_number)
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{
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$big_number = (string) $big_number;
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$current_numbers = [];
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for ($i = 0, $l = strlen($big_number); $i < $l; $i++) {
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if (!in_array($big_number[$i], $current_numbers, true)) {
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if (count($current_numbers) === 2) {
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return true;
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}
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$current_numbers = [$big_number[$i]];
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} else {
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$current_numbers[] = $big_number[$i];
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}
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}
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return count($current_numbers) === 2;
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}
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/**
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* @param int|string $big_number
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* @return bool
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*/
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function never_decrease($big_number)
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{
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$big_number = (string) $big_number;
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$current_number = null;
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for ($i = 0, $l = strlen($big_number); $i < $l; $i++) {
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if ($current_number > $big_number[$i]) {
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return false;
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}
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$current_number = $big_number[$i];
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}
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return true;
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}
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/**
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* @param int|string $number
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*
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* @return bool
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*/
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function is_valid($number)
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{
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return has_no_more_than_two_adjacent_number($number) && never_decrease($number);
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}
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$valids = [];
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for ($i = $min; $i <= $max; $i++) {
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if (is_valid($i)) {
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$valids[] = $i;
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}
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}
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echo count($valids); // more than 574 & less than 1099
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