数据结构常见算法代码实现1-PHP
（1）常用排序算法
Class MySort { /* * 所有排序均按升序排序 * */ /** * 插入排序 * @param $arr * @param $st * @param $ed * 通过将元素插入到已排序的序列中不断扩大已排序的序列 */ public function InsertSort(&$arr, $st, $ed) { for ($i = $st + 1; $i <= $ed; $i++) { $tmp = $arr[$i]; for ($j = $i - 1; $j >= $st; $j--) { if ($arr[$j] > $tmp) { // 如果元素比tmp大，就移动元素 $arr[$j + 1] = $arr[$j]; } else { break; } } $arr[$j + 1] = $tmp; } } /** * 冒泡排序 * @param $arr * @param $st * @param $ed * 通过不断交换相邻元素将更大的元素放在后边，一趟交换之后就能把最大的元素放到最后边，二趟排序可以把次大的元素放在 * 倒数第二的位置，n趟排序就可以把所有元素都放在正确的位置 */ public function BubbleSort(&$arr, $st, $ed) { for ($i = $ed - 1; $i >= $st; $i--) { $flag = false; for ($j = $st; $j <= $i; $j++) { if ($arr[$j] > $arr[$j + 1]) { $tmp = $arr[$j]; $arr[$j] = $arr[$j + 1]; $arr[$j + 1] = $tmp; $flag = true; } } if (!$flag) { // 优化：如果不发生交换，说明已排好序，退出即可 return; } } } /** * 选择排序 * @param $arr * @param $st * @param $ed * 每次选择当前未排序序列最小的元素放在合适的位置，已选择的最小元素构成了已排序序列，不断扩大已排序序列即可实现总体排序 */ public function SelectSort(&$arr, $st, $ed) { for ($i = $st; $i <= $ed; $i++) { $min = $i; for ($j = $i; $j <= $ed; $j++) { if ($arr[$min] > $arr[$j]) { $min = $j; } } if ($min != $i) { $tmp = $arr[$min]; $arr[$min] = $arr[$i]; $arr[$i] = $tmp; } } } /** * 归并排序 * @param $arr * @param $st * @param $ed * 归并排序的关键在于不断合并两个排好序的序列，可以通过递归实现 */ public function MergeSort(&$arr, $st, $ed) { if ($st < $ed) { $mid = floor(($st + $ed) / 2); // php数值默认使用float型计算，与Java和C不同，所以此处需要向下取整 $this->MergeSort($arr, $st, $mid); $this->MergeSort($arr, $mid + 1, $ed); $this->merge($arr, $st, $mid, $ed); } } /** * 归并数组arr a1-a2 b1-b2部分 * @param $arr * @param $a1 * @param $a2 * @param $b1 * @param $b2 */ private function merge(&$arr, $st, $mid, $ed) { $tmp_arr = array(); $a = $st; $b = $mid + 1; while ($a <= $mid && $b <= $ed) { if ($arr[$a] < $arr[$b]) { $tmp_arr[] = $arr[$a]; $a++; } else { $tmp_arr[] = $arr[$b]; $b++; } } while ($a <= $mid) { $tmp_arr[] = $arr[$a]; $a++; } while ($b <= $ed) { $tmp_arr[] = $arr[$b]; $b++; } for ($i = $st; $i <= $ed; $i++) { $arr[$i] = $tmp_arr[$i - $st]; } echo json_encode(func_get_args()) . "***********" . json_encode($tmp_arr) . "\n"; } /** * 快速排序 * @param $arr * @param $st * @param $ed */ public function QuickSort(&$arr, $st, $ed) { if ($st < $ed) { $mid = $this->partition($arr, $st, $ed); $this->QuickSort($arr, $st, $mid - 1); $this->QuickSort($arr, $mid + 1, $ed); } } /** * 对数组arr $sd-$ed部分使用轴元素进行划分 * @param $arr * @param $st * @param $ed * @return mixed */ private function partition(&$arr, $st, $ed) { $pivot = $arr[$st]; while ($st < $ed) { while ($st < $ed && $arr[$ed] > $pivot) $ed--; $arr[$st] = $arr[$ed]; while ($st < $ed && $arr[$st] <= $pivot) $st++; $arr[$ed] = $arr[$st]; } $arr[$st] = $pivot; return $st; } } $sort_obj = new MySort(); $arr = [2,9,6,4,0,3,1]; $sort_obj->MergeSort($arr, 0, 6); var_dump($arr);
（2）二分查找
Class MyFind { /** * 二分查找 * @param $arr * @param $key * PS: 必须保证输入的数组arr是升序排列的！ */ public function binarySearch($arr, $key) { $st = 0; $ed = count($arr) - 1; while ($st <= $ed) { $mid = floor(($st + $ed) / 2); if ($key == $arr[$mid]) { return $mid; } elseif ($key < $arr[$mid]) { $ed = $mid - 1; } else { $st = $mid + 1; } } return -1; } /** * 使用递归实现二分查找 * @param $arr * @param $key */ public function binarySearchWithRecursion($arr, $key) { return $this->recursion($arr, $key, 0, count($arr) - 1); } private function recursion($arr, $key, $st, $ed) { if ($st > $ed) { return -1; } $mid = floor(($st + $ed) / 2); if ($key == $arr[$mid]) { return $mid; } elseif ($key < $arr[$mid]) { return $this->recursion($arr, $key, $st, $mid - 1); } else { return $this->recursion($arr, $key, $mid + 1, $ed); } } /** * 二叉搜索树查找 * @param $root * @param $key * 二叉树结点定义： * class ListNode { * public $left; * public $right; * public $value; * } */ public function binaryTreeSearch($root, $key) { while ($root != null) { if ($key == $root->value) { return $root; } elseif ($key < $root->value) { $root = $root->left; } else { $root = $root->right; } } return null; } /** * 二分查找不小于$key的最小数（很多算法会用到，比如一致性哈希算法） * @param $arr * @param $key * 进行二分查找时，最后查找的位置总是最接近key的位置，如果key不存在，则最后查找的位置一定是小于key的最大数或者大于key的最小数 */ public function binarySearchMinSupper($arr, $key) { $st = 0; $ed = count($arr) - 1; while ($st <= $ed) { $mid = floor(($st + $ed) / 2); if ($key == $arr[$mid]) { return $arr[$mid]; } elseif ($key < $arr[$mid]) { $ed = $mid - 1; } else { $st = $mid + 1; } } return $key > $arr[$mid] ? $arr[$mid + 1] : $arr[$mid]; // 此处数组可能越界
} } $find_obj = new MyFind(); $arr = [0,1,2,3,4,6,9]; $a = $find_obj->binarySearchMinSupper($arr, 2.1); var_dump($a);
（3）栈与队列（顺序栈、链式栈、顺序队列、链式队列）
abstract Class MyStack { protected $capacity = -1; public function __construct($capacity = null) { if (isset($capacity)) { $this->capacity = $capacity; } } abstract public function push($val); abstract public function top(); abstract public function pop(); abstract public function isEmpty(); abstract public function isFull(); } Class MyArrayStack extends MyStack { //顺序栈 protected $arr = array(); public function push($val) { if ($this->isFull()) { return false; } $this->arr[] = $val; return true; } public function top() { return !$this->isEmpty() ? end($this->arr) : null; } public function pop() { return !$this->isEmpty() ? array_pop($this->arr) : null; } public function isEmpty() { return count($this->arr) == 0; } public function isFull() { if ($this->capacity == -1) { return false; } return count($this->arr) == $this->capacity; } } Class MyLinkedStackNode { public $val; public $next; } Class MyLinkedStack { //链式栈 protected $pointer = null; protected $count = 0; public function push($val) { if ($this->isFull()) { return false; } $node = new MyLinkedStackNode(); $node->val = $val; $node->next = $this->pointer; $this->pointer = $node; $this->count++; return true; } public function top() { return !$this->isEmpty() ? $this->pointer->val : null; } public function pop() { if ($this->isEmpty()) { return null; } $val = $this->pointer->val; $this->pointer = $this->pointer->next; $this->count--; return $val; } public function isEmpty() { return $this->count == 0; } public function isFull() { if ($this->capacity == -1) { return false; } return $this->count == $this->capacity; } } abstract Class MyQueue { protected $capacity = -1; public function __construct($capacity = null) { if (isset($capacity)) { $this->capacity = $capacity; } } abstract public function enqueue($val); abstract public function front(); abstract public function dequeue(); abstract public function isEmpty(); abstract public function isFull(); } Class MyArrayQueue extends MyQueue { protected $arr = array(); public function enqueue($val) { if ($this->isFull()) { return false; } $this->arr[] = $val; return true; } public function front() { return !$this->isEmpty() ? $this->arr[0] : null; } public function dequeue() { return !$this->isEmpty() ? array_shift($this->arr) : null; } public function isEmpty() { return count($this->arr) == 0; } public function isFull() { return count($this->arr) == $this->capacity; } } Class MyLinkedQueueNode { public $val; public $next; } Class MyLinkedQueue extends MyQueue { protected $head = null, $tail = null; protected $count = 0; public function enqueue($val) { if ($this->isFull()) { return false; } $node = new MyLinkedQueueNode(); $node->val = $val; if ($this->head == null) { //如果队列为空，效果等同于$this->isEmpty() $this->head = $this->tail = $node; } else { $this->tail->next = $node; $this->tail = $this->tail->next; } return true; } public function front() { return !$this->isEmpty() ? $this->head->val : null; } public function dequeue() { if ($this->isEmpty()) { return null; } $val = $this->head->val; if ($this->head == $this->tail) { //如果只有一个元素 $this->head = $this->tail = null; } else { $this->head = $this->head->next; } $this->count--; return $val; } public function isEmpty() { return $this->count == 0; } public function isFull() { return $this->count == $this->capacity; } }
