Merge pull request #322 from SHQHDMR/master

php实现跳表

php/17_skiplist/skipList.php

@@ -0,0 +1,108 @@
+<?php
+
+class SNode
+{
+    //数据域
+    public $data;
+
+    //指针域，引用SNode对象
+    public $next = [];
+
+    public function __construct($data = null)
+    {
+        $this->data = $data;
+    }
+
+    //获取当前节点索引层数
+    public function getMaxLevel()
+    {
+        return count($this->next) - 1;
+    }
+}
+
+class SkipList
+{
+    //索引最大层数
+    public $indexLevel;
+
+    //头节点
+    protected $head;
+
+    public function __construct(int $indexLevel)
+    {
+        $this->indexLevel = max($indexLevel, 0);
+        $this->head = new SNode();
+    }
+
+    public function addData($data)
+    {
+        $newNode = new SNode($data);
+        for ($level = $this->getRandomLevel(), $node = $this->head; $level >= 0; $level--) {
+            while (isset($node->next[$level]) && $data < $node->next[$level]->data) {
+                $node = $node->next[$level];
+            }
+            if (isset($node->next[$level])) {
+                $newNode->next[$level] = $node->next[$level];
+            }
+            $node->next[$level] = $newNode;
+        }
+        return $newNode;
+    }
+
+    public function deleteData($data)
+    {
+        $deleted = false;
+        for ($level = $this->head->getMaxLevel(), $node = $this->head; $level >= 0; $level--) {
+            while (isset($node->next[$level]) && $data < $node->next[$level]->data) {
+                $node = $node->next[$level];
+            }
+            if (isset($node->next[$level]) && $data == $node->next[$level]->data) {
+                $node->next[$level] = isset($node->next[$level]->next[$level]) ?
+                    $node->next[$level]->next[$level] : null;
+                $deleted = true;
+            }
+        }
+        return $deleted;
+    }
+
+    public function findData($data)
+    {
+        for ($level = $this->head->getMaxLevel(), $node = $this->head; $level >= 0; $level--) {
+            while (isset($node->next[$level]) && $data < $node->next[$level]->data) {
+                $node = $node->next[$level];
+            }
+            if (isset($node->next[$level]) && $data == $node->next[$level]->data) {
+                return $node->next[$level];
+            }
+        }
+        return false;
+    }
+
+    protected function getRandomLevel()
+    {
+        return mt_rand(0, $this->indexLevel);
+    }
+}
+
+/**
+ * 示例
+ */
+
+$indexLevel = 2;
+
+$skipList = new SkipList($indexLevel);
+
+for ($i = 10; $i >= 0; $i--) {
+    $skipList->addData($i);
+}
+
+//打印0到10组成的跳表
+var_dump($skipList);
+
+//返回SNode对象
+var_dump($skipList->findData(5));
+
+$skipList->deleteData(5);
+
+//返回false
+var_dump($skipList->findData(5));