몇 가지 일반적인 PHP 알고리즘 인터뷰 질문

function king($m, $n) { if (1 >= $n) { return $n; } $monkeys = range(1, $n); $count = $n; while ($count > 1) { $remainder = $m % $count; unset($monkeys[$remainder - 1]); $monkeys = array_values($monkeys); $count--; } return array_shift($monkeys); }

function cows ($n) { $cows = [1]; for ($i = 1; $i <= $n; $i++) { // 新出生的牛 $new_number = 0; foreach ($cows as $age => $num) { // 4岁到14岁的牛生育新的母牛 if ($age >= 3 & & $age < = 13) { $new_number += $num; } } // 将新出生的牛加到数组开头 array_unshift($cows, $new_number); // 取出数组的前20个单元 $cows = array_slice($cows, 0, 20); } return array_sum($cows); }

function bubble_sort ($array) { $array = array_values($array); for ($i = 0; $i < count($array); $i++) { for ($j = 0;$j < count($array) - $i - 1; $j++) { if ($array[$j] > $array[$j + 1]) { $temp = $array[$j + 1]; $array[$j + 1] = $array[$j]; $array[$j] = $temp; } } } return $array; }

function quick_sort ($array) { if (count($array) < = 1) { return $array; } $left_array = []; $right_array = []; $key = array_shift($array); foreach ($array as $value) { if ($key > $value) { $left_array[] = $value; } else { $right_array[] = $value; } } return array_merge(quick_sort($left_array), [$key], quick_sort($right_array)); }

function select_sort ($array) { $sort_array = []; while (count($array)) { $min = null; $min_key = null; foreach ($array as $key => $value) { if (is_null($min)) { $min = $value; $min_key = $key; } elseif ($min > $value) { $min = $value; $min_key = $key; } } $sort_array[] = $min; unset($array[$min_key]); } return $sort_array; }

function unique_char ($str) { $arr = array_unique(str_split($str)); sort($arr); return implode('', $arr); }

function all_file ($dir) { if (is_dir($dir)) { $resource = opendir($dir); while ($file = readdir($resource)) { if (in_array($file, ['.', '..'])) { continue; } elseif (is_dir($dir . '/' . $file)) { all_file($dir . '/' . $file); } else { echo $dir . '/' . $file, "\n"; } } } else { echo $dir, "\n"; } }

function ladder($steps) { return $steps < 2 ? 1 : ladder($steps - 1) + ladder($steps - 2); }

class Node { public $value; public $left; public $right; } /** * 先序遍历 根节点 ---> 左子树 ---> 右子树 * * @param $root */ function preorder ($root) { echo $root->value; if (!empty($root->left)) { preorder($root->left); } if (!empty($root->right)) { preorder($root->right); } } /** * 中序遍历，左子树---> 根节点 ---> 右子树 * * @param $root */ function inorder ($root) { if (!empty($root->left)) { inorder($root->left); } echo $root->value; if (!empty($root->right)) { inorder($root->right); } } /** * 后序遍历，左子树 ---> 右子树 ---> 根节点 * * @param $root */ function tailorder ($root) { if (!empty($root->left)) { tailorder($root->left); } if (!empty($root->right)) { tailorder($root->right); } echo $root->value; } $d = new Node; $d->value = 'D'; $b = new Node; $b->value = 'B'; $b->left = $d; $e = new Node; $e->value = 'E'; $f = new Node; $f->value = 'F'; $c = new Node; $c->value = 'C'; $c->left = $e; $c->right = $f; $a = new Node; $a->value = 'A'; $a->left = $b; $a->right = $c; preorder($a); echo "\n"; inorder($a); echo "\n"; tailorder($a); echo "\n";