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POBST recursivly position a node
 

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  1. POBST recursivly position a node
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    <p>I'm not particularly good at using recursion, but I felt the need to use it in this case. In my insertion method, I'm using a recursive retrieval method to set the node for insertion to the position desired (in this case, it should be positioning to root->right). Currently I'm using the insert method twice, and it fills root, but does not fill root->right. I'm using pass by reference in my arguments, so I'm really not sure why "found" isn't being set to root->right.</p> <pre><code>int Tree::insert_node(char artist[], char title[], char album[], int length) { // For adding a song node to the tree if(0 == root-&gt;a_song.is_empty()) { // If root is empty, fill it first root-&gt;a_song.set(artist, title, album, length); // Set the members of the node's song } else { // fill a leaf instead node* fill_node; // new node to be inserted retrieve(root, fill_node, artist, title); // set fill_node to it's proper position on the tree fill_node = new node; fill_node-&gt;left = NULL; fill_node-&gt;right = NULL; fill_node-&gt;a_song.set(artist, title, album, length); } //FOR TESTING, REMOVE LATER if(NULL == root-&gt;right) cout &lt;&lt; endl &lt;&lt; "RIGHT IS NULL" &lt;&lt; endl; // This is being output after the first AND second insert else cout &lt;&lt; endl &lt;&lt; "RIGHT IS NOT NULL" &lt;&lt; endl; return 0; } int Tree::retrieve(node* &amp; last, node* &amp; found, char artist[], char title[]) { //simple case: node*last is NULL, meaning found is set to the correct position if(NULL == last) { found = last; return 1; } else if(1 == last-&gt;a_song.compare(artist, title)) { // If artist or title is less, go left retrieve(last-&gt;left, found, artist, title); } else if(-1 == last-&gt;a_song.compare(artist, title)) { // If artist or title is greater, go right // I've tested, and the method is going to this case on the second insertion retrieve(last-&gt;right, found, artist, title); } else return 0; //zero indiciates the song you're trying to insert already exists } </code></pre>
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    1. PTQuestion
    1. This table or related slice is empty.
    1. USDan Minor
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    1. COyour code has a lot of problems. First of all, some cases of retrieve does not return a value. Also, when you set found to the correct position, you are only setting it to NULL. You should return a reference to the parent node, not the NULL.
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      1. POBST recursivly position a node
      1. USperreal
    2. COThanks, I changed my program to return the parent instead and it worked.
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      1. POBST recursivly position a node
      1. USDan Minor
 

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