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<?php |
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namespace leetcode\util; |
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class MinHeap |
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{ |
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private array $heap; |
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public function __construct() |
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{ |
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$this->heap = []; |
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} |
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public function push(int $val): void |
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{ |
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$this->heap[] = $val; |
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$this->siftUp(count($this->heap) - 1); |
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} |
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public function pop() |
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{ |
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if (empty($this->heap)) { |
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throw new \InvalidArgumentException('Min heap is empty'); |
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} |
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$leaf = array_pop($this->heap); |
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if (empty($this->heap)) { |
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return $leaf; |
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} |
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$value = $this->getRoot(); |
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$this->setRoot($leaf); |
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return $value; |
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} |
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public function count(): int |
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{ |
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return count($this->heap); |
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} |
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public function top() |
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{ |
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return current($this->heap); |
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} |
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public function compare(int $a, int $b): int |
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{ |
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return $a <=> $b; |
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} |
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public function getRoot(): int |
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{ |
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return $this->heap[0]; |
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} |
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public function setRoot(int $leaf): void |
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{ |
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$this->heap[0] = $leaf; |
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$this->siftDown(0); |
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} |
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private function siftUp(int $leaf): void |
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{ |
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while ($leaf > 0) { |
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$parent = $this->parent($leaf); |
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if ($this->compare($this->heap[$leaf], $this->heap[$parent]) > 0) { |
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break; |
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} |
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[$this->heap[$leaf], $this->heap[$parent]] = [$this->heap[$parent], $this->heap[$leaf]]; |
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$leaf = $parent; |
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} |
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} |
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private function siftDown(int $node): void |
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{ |
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$last = (int) floor(count($this->heap) / 2); |
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for ($parent = $node; $parent < $last; $parent = $leaf) { |
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$leaf = $this->getSmallestLeaf($parent); |
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if ($this->compare($this->heap[$parent], $this->heap[$leaf]) < 0) { |
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break; |
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} |
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[$this->heap[$leaf], $this->heap[$parent]] = [$this->heap[$parent], $this->heap[$leaf]]; |
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} |
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} |
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private function getSmallestLeaf(int $parent): int |
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{ |
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$left = $this->left($parent); |
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$right = $this->right($parent); |
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if ($right < count($this->heap) && $this->compare($this->heap[$left], $this->heap[$right]) > 0) { |
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return $right; |
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} |
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return $left; |
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} |
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private function left(int $index): int |
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{ |
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return ($index * 2) + 1; |
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} |
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private function right(int $index): int |
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{ |
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return ($index * 2) + 2; |
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} |
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private function parent(int $index): int |
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{ |
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return ($index - 1) / 2; |
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} |
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} |
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imajinyun /
leetcode-php
