简单HashTable实现

纸上得来终觉浅,所以我还是手动敲了一遍.懂了一点.2333333333333

直接看代码和注释:

<?php
/**
 * store the hash data
 */
class HashNode{
	public $key;
	public $value;
	public $nextNode;
	public function __construct($key,$value,$nextNode=null){
		$this->key = $key;
		$this->value = $value;
		$this->nextNode = $nextNode;
	}
}

class HashTable{
	# 存放数据
	private $buckets;
	# 数组大小
	private $size = 10;
	# 实例化时新建一个SPLFixedArray
	public function __construct(){
		# 使用SplFixedArray是因为其接近C语言的数组,效率也高
		# 使用该标准库函数需要给定一个数组大小
		$this->buckets = new SplFixedArray($this->size);
	}
	# hash enpty function 
	private function hashfunc($key){
		# count the key length
		$strlen = strlen($key);
		# total
		$hashval = 0;
		for ($i=0; $i < $strlen; $i++) { 
			# add the ascii of the word to total
			$hashval += ord($key{$i});
		}
		# return the remainder,serve as buckets key
		return ($hashval % $this->size);
	}
	# insert the value to the buckets
	public function insert($key,$val){
		# got the "$key" of the key
		$index = $this->hashfunc($key);
		# if this "$key" in the buckets have data,
		# insert the data to the hashnode,not buckets
		if(isset($this->buckets[$index]))
		{
			$newNode = new \HashNode($key,$val,$this->buckets[$index]);
			// print_r($newNode);
		}else{
			$newNode = new \HashNode($key,$val,null);
			// print_r($newNode);
		}
		$this->buckets[$index] = $newNode;
	}

	public function find($key){
		# got index by hanhfunc($key)
		$index = $this->hashfunc($key);
		# 英语不会了用回中文吧.
		# 拿当前这个key去取hashnode
		$current = $this->buckets[$index];
		while (isset($current)) {
			# 当前的对象的key和传进来的$key相同
			if($current->key == $key)
			{
				//find success
				//则查找成功
				return $current->value;
			}
			# 否则查找对象里nextNode
			$current = $current->nextNode;
		}
		# 查找失败
		return null;//find fail
		// return $this->buckets[$index];
	}


}

$hash = new HashTable();
# hash表冲突
# 原因:不同的关键字通过hash函数计算出来的hash值相同.
# 解决:开放定位法和拉链法
# 拉链法:
# 	将所有hash值相同的关键字节点链接在同一个链表中.
$hash->insert('test1','123456');
$hash->insert('test12','abcdef');
$hash->insert('test123','test123');

echo $hash->find('test1');
echo $hash->find('test12');