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<?php |
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declare(strict_types=1); |
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namespace leetcode; |
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use leetcode\util\ListNode; |
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class ReverseLinkedListII |
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{ |
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public static function reverseBetween(?ListNode $head, int $left, int $right): ?ListNode |
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{ |
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if (!$head || $left <= 0 || $right <= 0 || $left > $right) { |
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return null; |
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} |
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$dummy = new ListNode(); |
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$dummy->next = $head; |
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$prev = $dummy; |
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$curr = $dummy->next; |
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$i = 1; |
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while ($i < $left) { |
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$prev = $curr; |
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$curr = $curr->next; |
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$i++; |
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} |
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$node = $prev; |
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while ($i <= $right) { |
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$temp = $curr->next; |
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$curr->next = $prev; |
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$prev = $curr; |
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$curr = $temp; |
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$i++; |
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} |
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$node->next->next = $curr; |
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$node->next = $prev; |
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return $dummy->next; |
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} |
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public static function reverseBetween2(?ListNode $head, int $left, int $right): ?ListNode |
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{ |
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if (!$head || $left <= 0 || $right <= 0 || $left > $right) { |
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return null; |
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} |
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$dummy = new ListNode(); |
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$dummy->next = $head; |
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$prev = $dummy; |
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for ($i = 0; $i < $left - 1; $i++) { |
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$prev = $prev->next; |
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} |
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$tail = $prev->next; |
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for ($i = 0; $i < $right - $left; $i++) { |
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$temp = $prev->next; |
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$prev->next = $tail->next; |
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$tail->next = $tail->next->next; |
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$prev->next->next = $temp; |
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} |
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return $dummy->next; |
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} |
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public static function reverseBetween3(?ListNode $head, int $left, int $right): ?ListNode |
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{ |
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if (!$head || $left <= 0 || $right <= 0 || $left > $right) { |
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return null; |
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} |
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$dummy = new ListNode(); |
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$dummy->next = $head; |
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$prev = $dummy; |
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for ($i = 1; $i < $left; $i++) { |
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$prev = $prev->next; |
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} |
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$node = $prev->next; |
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for ($i = $left; $i < $right; $i++) { |
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self::swap($prev, $node->next); |
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self::swap($prev, $node); |
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} |
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return $dummy->next; |
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} |
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public static function reverseBetween4(?ListNode $head, int $left, int $right): ?ListNode |
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{ |
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if (!$head || $left <= 0 || $right <= 0 || $left > $right) { |
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return null; |
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} |
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if ($left === $right) { |
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return $head; |
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} |
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if ($left > 1) { |
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$node = $head; |
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$node->next = self::reverseBetween4($head->next, $left - 1, $right - 1); |
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return $node; |
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} else { |
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$next = $head->next; |
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$node = self::reverseBetween4($next, 1, $right - 1); |
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$tail = $next->next; |
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$next->next = $head; |
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$head->next = $tail; |
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return $node; |
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} |
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} |
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private static function swap(ListNode $p, ListNode $q) |
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{ |
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$t = $p->next; |
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$p->next = $q->next; |
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$q->next = $t; |
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} |
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} |
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imajinyun /
leetcode-php
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