Detailed explanation of depth-first search algorithm implemented in PHP

This article mainly introduces the implementation of depth-first search algorithm (DFS, Depth First Search) in PHP. It briefly analyzes the principle of depth-first search algorithm and combines specific examples to give the specific steps and related operations of PHP to implement depth-first search. For tips, friends who need them can refer to

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Implementation principle of depth-first search:

Implementation code:

<?php
class Search_Method
{
  //无向图的数组描述
  private $dfs_save;
  //全局记录数组
  private $arr;
  //控制分支-
  private $k = 0;
  public function __construct()
  {
    $this->dfs_save = array(
      array(0,1,1,1,0,0,0,0,0),
      array(1,0,0,0,1,0,0,0,0),
      array(1,0,0,0,0,1,0,0,0),
      array(1,0,0,0,0,0,1,0,0),
      array(0,1,0,0,0,1,0,0,1),
      array(0,0,1,0,1,0,0,1,0),
      array(0,0,0,1,0,0,0,0,0),
      array(0,0,0,0,0,1,0,0,0),
      array(0,0,0,0,1,0,0,0,0),
    );
    $this->arr = array();
  }
  //深度优先搜索的递归实现方法
  public function dfs($v)
  {
    //对顶点做一些操作
    echo str_repeat("-",$this->k);
    echo &#39;V&#39;.($v+1).&#39;<br>&#39;;
    //记录已访问的顶点
    $this->arr[]= $v;
    //查找与顶点相连接的顶点，如果存在就继续深度优先搜索
    for($i=0;$i<9;$i++)
    {
      if(!in_array($i,$this->arr)&&$this->dfs_save[$v][$i]==1)
      {
        $this->k++;
        $this->dfs($i);
      }
    }
    $this->k--;
    return;
  }
}
?>

Achieve output results:

V1
-V2
--V5
---V6
----V3
----V8
---V9
-V4
--V7

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