I'm creating a skip list program for my Algorithms and Advanced Data Structure class. I was tasked with implementing a find & add method for the skiplist. Here is my program, I'm running into a segmentation fault when I add my second value into the skiplist. My first issue that I fixed was that I wasn't checking the first node in the list to see if it was nullptr, but that was not my only issue apparently.

Add Method:

void SkipList::add(const ElemType &el) {

// Create a new node with the given element

Node *newNode = new Node(el);

// Get the height of the new node

int newHeight = newNode->nodeHeight;

// If the height of the new node is greater than the current list height,

// update the list height.

if (newHeight > listHeight) {

listHeight = newHeight;

}

// Array to keep track of nodes to update

Node *update[MAX_NUM_LISTS];

// Start from the top level

Node *current = head[listHeight - 1]; // Initialize current correctly

// If the list is empty, assign the first node to head

if (head[0] == nullptr) {

head[0] = newNode;

} else {

// Loop to traverse through list

for (int i = listHeight - 1; i >= 0; i--) {

// Move forward in the current level

while (current->next[i] != nullptr && current->next[i]->elem < el) {

current = current->next[i];

}

// Store the node before which the new node should be inserted

update[i] = current;

}

// Insert the new node at each level

for (int i = 0; i < newHeight; i++) {

newNode->next[i] = update[i]->next[i];

update[i]->next[i] = newNode;

}

}

}

Find Method:

bool SkipList::find(const ElemType &el) const {

// Start from the top level

Node *current = head[listHeight - 1];

bool found = false;

// Iterate through the levels of the skip list

for (int i = listHeight - 1; i >= 0; i--) {

// Move forward in the current level until reaching the end or finding a larger element

while (current->next[i] != nullptr && current->next[i]->elem < el) {

current = current->next[i];

}

// Check if the current node's next node contains the target element

if (current->next[i] != nullptr && current->next[i]->elem == el) {

found = true; // Element found

}

}

return found; // Element not found in the skip list

}

Main:

int main()

{

ElemType inputs[] = {5, 7, 8, 10, 12, 17, 19, 22, 28, 31, 33, 35, 42, 51, 59};

SkipList list1;

cout << "For list1 (same as in the slide 10 of Skip List1 Lecture Note):\n";

// for (int i=0; i

for (int i = 0; i < static_cast(std::size(inputs)); i++)

{

cout << "add " << inputs[i] << endl;

list1.add(inputs[i]);

cout << "list1:\n"

<< list1 << endl;

}

if (list1.find(33))

cout << "33 is found!\n";

else

cout << "33 is not found!!!!\n";

if (list1.find(70))

cout << "70 is found!\n";

else

cout << "70 is not found!!!!\n";

if (list1.find(10))

cout << "10 is found!\n";

else

cout << "10 is not found!!!!\n";

cout << "\n===================================\n";

cout << "For list2:\n";

ElemType inputs2[] = {19, 8, 17, 59, 12, 7, 5, 22, 28, 35, 33, 31, 42, 51, 10};

SkipList list2;

for (int i = 0; i < static_cast(std::size(inputs2)); i++)

{

cout << "add " << inputs2[i] << endl;

list2.add(inputs2[i]);

cout << "list2:\n"

<< list2 << endl;

}

if (list2.find(33))

cout << "33 is found!\n";

else

cout << "33 is not found!!!!\n";

if (list2.find(70))

cout << "70 is found!\n";

else

cout << "70 is not found!!!!\n";

if (list2.find(10))

cout << "10 is found!\n";

else

cout << "10 is not found!!!!\n";

return 0;

}