• 递归的两种模式——取得文件目录树

    递归是个神奇的东西，有时明白，有时候不明白。

    写的多了便会总结。

    总结两种常用的模式：

    • 队列递归
    • 级联递归

    简单的说，一个是返回平坦的队列，一个是返回有层级关系的Map。以取得文件的目录树为例：

     1 #    取得文档整体目录树    
 2 function tree( $path ,  $cutfix = 0 , $regexp = '/.*/' ,  $flat = 0 , $result = array() ,  $level = 0 ){
 3     $level = $level+1;
 4     $dirs  = scandir( $path );
 5     foreach($dirs as $d) {
 6         $realpath = joinp( $path ,$d );
 7         $current  =  array();
 8         if( !is_dir($realpath) ){ continue ;}
 9         if ($d == '.' || $d == '..') {}
10         else if( preg_match( $regexp , $d ) ){
11             if( is_int( $flat ) ){
12                 $id = $this->gid('tree');
13                 $result[] = array( 'id'=>$id,  'pid'=> $flat, 'name' => $d , 'path' => substr( $realpath ,$cutfix ),'level'=>$level );
14                 $result   = $result + $this -> tree( $realpath  ,$cutfix , $regexp, $id , $result ,$level);
15             }else{
16                 $result[] =  array( 'name' => $d , 'path' => substr( $realpath ,$cutfix ) , 'child' => $this->tree( $realpath ,$cutfix , $regexp  , $flat ,$result  )  );
17             }
18         }
19     }
20     return $result;
21 }

    队列递归返回：

    [
    •  
      {
      • id: 1,
      • pid: 0,
      • name: "first-1",
      • path: "/first-1",
      • level: 1
      },
    •  
      {
      • id: 2,
      • pid: 1,
      • name: "sec-do",
      • path: "/first-1/sec-do",
      • level: 2
      },
    •  
      {
      • id: 3,
      • pid: 0,
      • name: "first-2",
      • path: "/first-2",
      • level: 1
      },
    •  
      {
      • id: 4,
      • pid: 3,
      • name: "sec-2-1",
      • path: "/first-2/sec-2-1",
      • level: 2
      },
    •  
      {
      • id: 5,
      • pid: 3,
      • name: "sec-2-2",
      • path: "/first-2/sec-2-2",
      • level: 2
      },
    •  
      {
      • id: 6,
      • pid: 5,
      • name: "thr",
      • path: "/first-2/sec-2-2/thr",
      • level: 3
      }
    ]

    级联递归返回

    [
    •  
      {
      • name: "first-1",
      • path: "/first-1",
      • child: 
         
        [
        •  
          {
          • name: "sec-do",
          • path: "/first-1/sec-do",
          • child: [ ]
          }
        ]
      },
    •  
      {
      • name: "first-2",
      • path: "/first-2",
      • child: 
         
        [
        •  
          {
          • name: "first-1",
          • path: "/first-1",
          • child: 
             
            [
            •  
              {
              • name: "sec-do",
              • path: "/first-1/sec-do",
              • child: [ ]
              }
            ]
          },
        •  
          {
          • name: "sec-2-1",
          • path: "/first-2/sec-2-1",
          • child: 
             
            [
            •  
              {
              • name: "first-1",
              • path: "/first-1",
              • child: 
                 
                [
                •  
                  {
                  • name: "sec-do",
                  • path: "/first-1/sec-do",
                  • child: [ ]
                  }
                ]
              }
            ]
          },
        •  
          {
          • name: "sec-2-2",
          • path: "/first-2/sec-2-2",
          • child: 
             
            [
            •  
              {
              • name: "first-1",
              • path: "/first-1",
              • child: 
                 
                [
                •  
                  {
                  • name: "sec-do",
                  • path: "/first-1/sec-do",
                  • child: [ ]
                  }
                ]
              },
            •  
              {
              • name: "sec-2-1",
              • path: "/first-2/sec-2-1",
              • child: 
                 
                [
                •  
                  {
                  • name: "first-1",
                  • path: "/first-1",
                  • child: 
                     
                    [
                    •  
                      {
                      • name: "sec-do",
                      • path: "/first-1/sec-do",
                      • child: [ ]
                      }
                    ]
                  }
                ]
              },
            •  
              {
              • name: "thr",
              • path: "/first-2/sec-2-2/thr",
              • child: 
                 
                [
                •  
                  {
                  • name: "first-1",
                  • path: "/first-1",
                  • child: 
                     
                    [
                    •  
                      {
                      • name: "sec-do",
                      • path: "/first-1/sec-do",
                      • child: [ ]
                      }
                    ]
                  },
                •  
                  {
                  • name: "sec-2-1",
                  • path: "/first-2/sec-2-1",
                  • child: 
                     
                    [
                    •  
                      {
                      • name: "first-1",
                      • path: "/first-1",
                      • child: 
                         
                        [
                        •  
                          {
                          • name: "sec-do",
                          • path: "/first-1/sec-do",
                          • child: [ ]
                          }
                        ]
                      }
                    ]
                  }
                ]
              }
            ]
          }
        ]
      }
    ]
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  • 原文地址：https://www.cnblogs.com/webooxx/p/2777362.html
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