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copied!<p><strong>For <code>insert</code>:</strong></p> <p>About these lines:</p> <pre><code>while(head->next->priority >= priority) head = head->next; </code></pre> <ul> <li><p>If <code>head</code> is <code>NULL</code>, that's not going to work. This may not actually be a problem if <code>head</code> can never be <code>NULL</code> for whichever reason (e.g. it has a dummy element as gruszczy mentioned).</p></li> <li><p>You're changing <code>head</code>, thus you're getting rid of the first few elements every time you insert. You probably need a temp variable.</p></li> <li><p>You need to also have a <code>NULL</code> check in case you reach the end of the list.</p></li> </ul> <p>So, we get:</p> <pre><code>struct process *temp = head; while (temp->next != NULL && temp->next->priority >= priority) temp = temp->next; </code></pre> <p><strong>For <code>pop</code>:</strong></p> <p>If the first element isn't a dummy element, then you should be returning the ID of <code>head</code>, not <code>head->next</code> (and you were trying to return a value of an already freed variable - this is undefined behaviour).</p> <pre><code>if (head == NULL) return -1; int id = head->id; struct process *temp = head; head = head->next; free(temp); return id; </code></pre> <p><strong>For <code>popId</code>:</strong></p> <ul> <li><p>You're checking <code>ptr</code>'s ID, but, if it's the one we're looking for, you're removing the next element rather than <code>ptr</code>. You should be checking the next one's ID.</p></li> <li><p><code>head == NULL</code> would again need to be a special case.</p></li> <li><p>The <code>free</code> should be in the if-statement. If it isn't, you need to cater for it not being found or finding multiple elements with the same ID.</p></li> <li><p>You should break out of the loop in the if-statement if there can only be one element with that ID, or you want to only remove the first such element.</p></li> </ul> <p>I'll leave it to you to fix, but here's a version using double-pointers.</p> <pre><code>void popId(int id) { struct process **ptr = &head; while (*ptr != NULL) { if ((*ptr)->id == id) { struct process *temp = *ptr; *ptr = (*ptr)->next; free(temp); } else { prt = &(*ptr)->next; } } } </code></pre> <p>Note that the above code doesn't break out of the loop in the if-statement. This can be added if you're guaranteed to only have one element with some given ID in the list, or you want to just delete the first such element.</p>

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