dongyong1400 2017-05-18 09:51
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PHP递归函数问题

I need to traverse the following type of structures:

            P
        /   |   \
    E1      E2     E3 .....
   / \     /  \    |
  V1  V2  V1  V2   V3  .....
  |   |   |   |    / \
  T1  T2  T3  T4  T5  T6 .....

In order to form an associative array with the following elements:

        V1(key) = [T1(E1), T3(E2), ...]
        V2(key) = [T2(E1), T4(E2), ...]
        V3(key) = [T5(E3), T6(E3), ...]
        .....

Now here comes the tricky part: the structure is actually simplified. I don't know beforehand how many E-level nodes I'll actually need to deal with (3 in the drawing), or how many V-level nodes each of them has (but at least 1 will be there), and furthermore, each V-level node may also have multiple T-nodes.

I tried using a recursion function to do this (in PHP). I'll simplify the code because it has weird methods regarding some objects that don't really matter to the discussion. My current attempt results in:

        V1(key) = [T1(E1)]
        V2(key) = [T2(E1)]

That I think means that the traversal is only occurring going down the first E-level "branch".

This is my code:

$result = [];

$traverser = function($node) use (&$traverser, &$result) {
  $children = $node->getChildrenArray();

  foreach($children as $key=>$child){
    if ($child->nodeType() == 'v_node') {
      $v_node_key = $child->name;

      $t_nodes = $child->getChildrenArray();

        if ( !array_key_exists($v_node_key, $results) ){
          $results[$v_node_key] = [];
        }

        foreach($t_nodes as $keyt=>$t_node) {
          $info_array = $t_node->toArray();
          array_push($results[$v_node_key], $info_array);
        }

    } else if ($child->nodeType() == 'e_node') {
        // keep digging
        return $traverser($child);
    }

  }
};

$traverser($p_node); 

I think the problem is that once I call the $traverser function within the foreach it won't come back and resume from the previous state.

Can anyone advise on how I should be tackling this to get the result I placed above?

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  • dongxiao1591 2017-05-18 11:33
    关注

    Well, this is a bit awkward and I'm still not entirely sure if this is the right motive, but I solved this by removing the return in my code.

    I thought that the return would allow me to exit the nested function call, but rather I think it jumped out of the first function call (the $traverser($p_node); line).

    Even so, by changing the return $traverser($child); line to $traverser($child); it did what it had to do.

    Hope this helps anyone!

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