php 求解最长公共前缀（字典树）

leetcode 题解

<?php
class Solution
{

    /**
     * @param String[] $strs
     * @return String
     */
    public function longestCommonPrefix($strs)
    {
        if (empty($strs)) {
            return "";
        }
        foreach ($strs as  $value) {
            if(empty($value)){
                return "";
            }
        }
        if(!isset($strs[1])){
            return $strs[0];
        }
        $head = new Node();
        foreach ($strs as  $str) {
            // 加入字典树
            $this->addString($head, $str);
        }
        
        // 获取公共最长前缀
        $a = $this->getMaxComPrex($head);
        return $a;
    }

        /* 获取所有字符串--递归 */
        public function getMaxComPrex($node, $str_array = array(), $str = '')
        {
   
            if (count($node->childNode)>1) {
                return $str;
            } else {
                foreach ($node->childNode as $k => $v) {
                    if ($v->is_end == true) {
                        return  $str. $v->value;
                    }
                    $str = $this->getMaxComPrex($v, $str_array, $str . $v->value);
                }
                return $str;
            }
        }

    /* 添加字符串 */
    public function addString(&$head, $str)
    {
        $node = null;
        for ($i=0; $i < strlen($str); $i++) {
            if ($str[$i] != '') {
                $is_end = $i != (strlen($str) - 1) ? false : true;
                if ($i == 0) {
                    $node = $head->addChildNode($str[$i], $is_end);
                } else {
                    $node = $node->addChildNode($str[$i], $is_end);
                }
            }
        }
    }
}

class Node
{
    public $value;
    public $is_end=false;
    public $childNode;

    public function addChildNode($value, $is_end=false)
    {
        $node = $this->searchChildNode($value, $is_end);
        if (empty($node)) {
            // 不存在节点，添加为子节点
            $node = new Node();
            $node->value = $value;
            $this->childNode[] = $node;
        }
        if($node->is_end==false){
            $node->is_end = $is_end;
        }
        return $node;
    }

    /* 查询子节点 */

    public function searchChildNode($value)
    {
        foreach ($this->childNode as $k => $v) {
            if ($v->value == $value) {
                //  存在节点，返回该节点
                return $this->childNode[$k];
            }
        }
    }
}


$k = ["aaa","aa","aaa"];
//$k = ["ab","a"];

$s = new Solution();
$s->longestCommonPrefix($k);