Databases
StackOverflow2013
Postsdbo
POHow can an element find its own index in a vector?
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POHow can an element find its own index in a vector?
    primarykey
    data
    text
    <p>I'm trying to reimplement a tree data structure using <code>std::unique_ptr</code>, and the idea is that the parent node would own its children, who are stored in a vector of <code>unique_ptr</code>.</p> <p>For interface reasons, I need a method where the node destroys itself. In this case, I think the node to erase itself from the children vector in its parent.</p> <p>The following implementation 'works' (in a c++11 compiler), but it is ugly as hell and I'm sure it is a sub optimum way of dealing with this problem.</p> <pre><code>#include &lt;iostream&gt; #include &lt;memory&gt; #include &lt;vector&gt; #include &lt;algorithm&gt; struct Node { typedef std::vector&lt;std::unique_ptr&lt;Node&gt;&gt; vec_node_uptr; unsigned id; Node* parent; vec_node_uptr child_nodes; // ctor Node(unsigned id): id(id){ parent = nullptr; } void add_child(Node* new_child){ new_child -&gt; parent = this; child_nodes.push_back( std::unique_ptr&lt;Node&gt;(std::move(new_child) ) ); } int where_am_i(){ int result_ = 0; for(auto&amp; i: this -&gt; parent -&gt; child_nodes) { if (this == i.get()) { return result_; } else { result_++; } } } void suicide(){ parent -&gt; child_nodes.erase(parent -&gt; child_nodes.begin()+ where_am_i()); } }; int main() { std::unique_ptr&lt;Node&gt; root(new Node(0)); root -&gt; add_child(new Node(1)); root -&gt; add_child(new Node(2)); root -&gt; child_nodes[0] -&gt; add_child(new Node(3)); root -&gt; child_nodes[0] -&gt; add_child(new Node(4)); root -&gt; child_nodes[1] -&gt; add_child(new Node(5)); root -&gt; child_nodes[1] -&gt; add_child(new Node(6)); root -&gt; child_nodes[1] -&gt; suicide(); return 0; } </code></pre> <p>Any suggestions? Maybe using <code>std::find</code>? </p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USdudu
    1. USdudu
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POHow can an element find its own index in a vector?
      1. This table or related slice is empty.
      1. VTUpMod
    1. COI think this question would be better suited for [codereview.se]
      singulars
      1. POHow can an element find its own index in a vector?
      1. USDoorknob
    2. COI would move the responsibility to the parent. The child would call parent->remove_child(this)
      singulars
      1. POHow can an element find its own index in a vector?
      1. USEnigma
    3. CO@Enigma: OK, but the fundamental problem of finding the child remains unchanged. All that changes is the location of the source code that does it :-P
      singulars
      1. POHow can an element find its own index in a vector?
      1. USj_random_hacker
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload