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POC++ linked binary search tree (DeleteTree)
 

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  1. POC++ linked binary search tree (DeleteTree)
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    <p>I have to implement a binary search tree using C++ for one of assignments. I've created the class, and attempted to implement the <strong>InsertItem, PrintTree, DeleteTree</strong> methods for the class, I think I did everything right but for some reason my program keeps crashing :(</p> <p>Here's my code:</p> <p><strong>PrintTree Method</strong></p> <pre><code>template &lt;class TItem&gt; void BinarySearchTree&lt;TItem&gt;::PrintTree() { PrintTree(RootNode); } template &lt;class TItem&gt; void BinarySearchTree&lt;TItem&gt;::PrintTree(BinarySearchTreeNode* Node) { if(Node == NULL) return; cout &lt;&lt; Node-&gt;Data &lt;&lt; endl; PrintTree(Node-&gt;LeftChild); PrintTree(Node-&gt;RightChild); } </code></pre> <p><strong>DeleteTree Method</strong></p> <pre><code>template &lt;class TItem&gt; void BinarySearchTree&lt;TItem&gt;::DeleteTree() { DeleteTree(RootNode); } template &lt;class TItem&gt; void BinarySearchTree&lt;TItem&gt;::DeleteTree(BinarySearchTreeNode* Node) { if(Node == NULL) return; DeleteTree(Node-&gt;LeftChild); DeleteTree(Node-&gt;RightChild); delete Node; } </code></pre> <p><strong>My sequence of method calls up until the program crashes:</strong></p> <p>I insert items <code>F,B,G,A,D,I,C,E,H</code>: <strong>works fine</strong></p> <p>I call <code>PrintTree()</code>: <strong>works fine</strong></p> <p>I call <code>DeleteTree()</code>: <strong>works fine</strong></p> <p>I call <code>PrintTree()</code> again: <strong>program crashes</strong></p> <p>For some reason the expression <code>if(RootNode == NULL)</code> is not returning true after the <code>DeleteTree()</code> method is called, so the program tries to print something that doesn't exist and crashes. I'm not sure why this is happening, what am I doing wrong here?</p> <p>Any and all help is appreciated. </p>
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    1. USSaad Imran.
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    1. COthis seems to be a dangling pointer : calling `delete p ;` on a pointer does not set it to 0. So in the end the memory pointed by `RootNode` is freed by the last call to `delete Node ;`. You should add `RootNode = 0 ;` in the end of `::DeleteTree()`
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    2. COHey, this worked. Thanks!
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      1. USSaad Imran.
    3. CO@totem - this solves the problem for the `DeleteTree()` method, but not if you pass in a specific node that isn't `RootNode` to `DeleteTree(*Node)`
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      1. USBrian Roach
 

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