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copied!<p>The reason why the code segfaults when you uncomment the printf statement is because rootNode is a NULL pointer. Dereferencing this NULL pointer in the function call causes the segfault.</p> <p>The reason that rootNode is a NULL pointer is that it is never changed by the code. Calling <code>insertNode()</code> results in the local variable <code>n</code> being set to the value that is stored in <code>rootNode</code> (in this case NULL). The changes to <code>n</code> in the <code>insertNode()</code> function do not change <code>rootNode</code>. </p> <p>To fix the code you could change the <code>insertNode</code> and <code>deleteNode</code> functions to accept a pointer to the root node pointer. For example the <code>insertCode()</code> function would become:</p> <pre><code>void insertNode(int i, node **n) { if(*n == NULL) { (*n) = (node*)malloc(sizeof(node)); (*n)->leftChildNode = NULL; (*n)->rightChildNode = NULL; (*n)->data = i; } else { if((*n)->data == i) { printf("\nThis value already exists in the tree!"); } else { if(i > (*n)->data) insertNode(i, &(*n)->rightChildNode); else insertNode(i, &(*n)->leftChildNode); } } } </code></pre> <p>You would also have to change the code to call <code>insertNode()</code> with a reference to rootNode <code>insertNode(num, &rootNode);</code></p> <p>I also recommend that you check the return values of the various scanf calls. If <code>scanf("%d",x)</code> returns 0 then the value not be converted to an int and the contents of x are undefined. Ideally the code would handle this case gracefully. </p>

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