Class TreeNode { public int $val; public ?TreeNode $left = null; public ?TreeNode $right = null; public function __construct(int $x) { $this->val = $x; } } Class Solution { public function preorderTraversal(TreeNode $root) : ?array { if (empty($root)) return []; $stack = [$root]; $output = array(); while (boolval($stack)) { $root = array_pop($stack); if (boolval($root)) { array_push($output, $root->val); if (boolval($root->right)) { array_push($stack, $root->right); } if (boolval($root->left)) { array_push($stack, $root->left); } } } return $output; } public function inorderTraversal(TreeNode $root) : ?array { $stack = $output = array(); $curr = $root; while (boolval($curr) || boolval($stack)) { while (boolval($curr)) { array_push($stack, $curr); $curr = $curr->left; } $curr = array_pop($stack); array_push($output, $curr->val); $curr = $curr->right; } return $output; } public function postorderTraversal(TreeNode $root) : ?array { if (empty($root)) return []; $stack = [$root]; $output = array(); while (boolval($stack)) { $root = array_pop($stack); if (boolval($root)) { array_push($output, $root->val); if (boolval($root->left)) { array_push($stack, $root->left); } if (boolval($root->right)) { array_push($stack, $root->right); } } } return array_reverse($output); } } $first = new TreeNode(1); $second = new TreeNode(2); $third = new TreeNode(3); $first->right = $second; $second->left = $third; $solution = new Solution(); $result['pre'] = $solution->preorderTraversal($first); $result['in'] = $solution->inorderTraversal($first); $result['post'] = $solution->postorderTraversal($first); print_r($result);
Array ( [pre] => Array ( [0] => 1 [1] => 2 [2] => 3 ) [in] => Array ( [0] => 1 [1] => 3 [2] => 2 ) [post] => Array ( [0] => 3 [1] => 2 [2] => 1 ) ) [Process exited 0]
本作品採用《CC 協議》，轉載必須註明作者和本文連結