How to delete a node in a linked list? - c++

Question

This is what I have so far, but it's not working. Basically skips to else if(cnode == preposition).
void LinkedList::Delete(Node *PrePosition) {
Node *cnode = head;
Node *pnode = NULL;
while (cnode != NULL) {
if (cnode->value != NULL) {
if (pnode == NULL) {
// if there is not previous node
head = cnode->next;
}
else if (cnode == PrePosition) {
// if there is previous node
cout << endl << "Deleting: " << cnode << endl;
pnode->next = cnode->next;
}
}
else {
// don't delete
pnode = cnode;
}
cnode = cnode->next;
}
}

Answer 1

1: Take the pointer from the previous node and point it to the next one after the one you want to delete
2: Delete the pointer from the previous node to the current node
3: Delete the pointer from the next node to the current node (if it is a doubly-linked list)

Answer 2

Three cases of delete in a singly linked-list:
delete the first node
void delete_first()
{
node *temp=new node;
temp=head;
head=head->next;
delete temp;
}
delete the last node
void delete_last()
{
node *current = new node;
node *previous = new node;
current=head;
while(current->next != NULL)
{
previous = current;
current = current->next;
}
tail = previous; // if you have a Node* tail member in your LinkedList
previous->next = NULL;
delete current;
}
delete at a particular position (your case)
void LinkedList::delete_position(int pos)
{
node *current=new node;
node *previous=new node;
current=head;
for(int i=1; i < pos; i++) //or i = 0; i < pos-1
{
previous=current;
current=current->next;
}
previous->next=current->next;
delete current;
}
^^ from codementor ^^
However if your function signature intends delete_node(Node* nodeToDelete) [PrePosition is not a good name in this case] and you want delete the node passed to the function without knowing its position in the list we can modify delete_position() like so:
void LinkedList::delete_node(Node* nodeToDelete)
{
node *current= head;
node *previous= nullptr;
if (head == nodeToDelete){
head = nodeToDelete->next;
delete nodeToDelete;
return
}//else
while(current != nodeToDelete)
{
previous = current;
current = current->next
}
previous->next = current->next;
delete nodeToDelete;
}
Also in your original code, if it's skipping the line you mentioned, pnode is always null when cnode has a non-null value in it.

Answer 3

Here are the full code
class SportShoe {
private:
struct nodeSport {
int ShoeID;
char BrandShoe[SIZE];
char TypeShoe[SIZE];
char ColourShoe[SIZE];
int SizeShoe;
float PriceShoe;
nodeSport *last;
};
nodeSport *first = NULL;
public:
int MenuSportShoe();
void AddSportShoe();
void DisplaySportShoe();
void DeleteSportShoe();
static void ExitSportShoe();
};
int SportShoe::MenuSportShoe() {
int OptionSportShoe = 0;
cout << endl;
cout << "Please select from the menu:" << endl;
cout << ":: 1 :: Add item to shoe list" << endl;
cout << ":: 2 :: Display shoes list" << endl;
cout << ":: 3 :: Delete item from the list" << endl;
cout << ":: 4 :: Back" << endl;
cout << "=>> ";
cin >> OptionSportShoe;
while (OptionSportShoe == 1){
AddSportShoe();
}
while (OptionSportShoe == 2){
DisplaySportShoe();
}
while (OptionSportShoe == 3){
DeleteSportShoe();
}
while (OptionSportShoe == 4){
ExitSportShoe();
}
return 0;
}
void SportShoe::AddSportShoe() {
nodeSport *tempShoe1, *tempShoe2;
tempShoe1 = new nodeSport;
cout << "Please enter the Shoe ID : (eg. 43210) " << endl;
cout << "=>> ";
cin >> tempShoe1->ShoeID;
cout << "Please enter the Shoe Brand: (eg. Adidas) " << endl;
cout << "=>> ";
cin.sync();
cin.getline(tempShoe1->BrandShoe,SIZE);
cout << "Please enter the Shoe Type : (eg. Running) " << endl;
cout << "=>> ";
cin.sync();
cin.getline(tempShoe1->TypeShoe,SIZE);
cout << "What is the Shoe Colour : (eg. Grey) " << endl;
cout << "=>> ";
cin.sync();
cin.getline(tempShoe1->ColourShoe,SIZE);
cout << "Please enter Shoe Size : (eg. 9) " << endl;
cout << "=>> ";
cin >> tempShoe1->SizeShoe;
cout << "Please enter the price of the Shoe : (eg. RM123.45) " << endl;
cout << "=>> RM ";
cin >> tempShoe1->PriceShoe;
tempShoe1->last = NULL;
if (first == NULL)
first = tempShoe1;
else
{
tempShoe2 = first;
while (tempShoe2->last != NULL)
tempShoe2 = tempShoe2->last;
tempShoe2->last = tempShoe1;
}
system("PAUSE");
MenuSportShoe();
}
void SportShoe::DisplaySportShoe() {
nodeSport *tempShoe1;
tempShoe1 = first;
while(tempShoe1){
cout << "ID : " << tempShoe1->ShoeID << endl;
cout << "Brand : " << tempShoe1->BrandShoe << endl;
cout << "Type : " << tempShoe1->TypeShoe << endl;
cout << "Colour : " << tempShoe1->ColourShoe << endl;
cout << "Size : " << tempShoe1->SizeShoe << endl;
cout << "Price : " << tempShoe1->PriceShoe << endl;
cout << endl;
tempShoe1 = tempShoe1->last;
}
system("PAUSE");
MenuSportShoe();
}
void SportShoe::DeleteSportShoe(){
nodeSport *tempShoe1, *tempShoe2;
int DataShoe;
tempShoe2 = tempShoe1 = first;
if(tempShoe1 == NULL)
{
cout << "\nList is empty!" << endl;
system("PAUSE");
MenuSportShoe();
}
while(tempShoe1 != NULL)
{
cout << "\nEnter the Shoes ID to be deleted: (eg. 123) ";
cin >> DataShoe;
tempShoe2 = tempShoe1;
tempShoe1 = tempShoe1->last;
if(DataShoe == tempShoe1-> ShoeID){
if(tempShoe1 == first) {
first = first->last;
cout << "\nData deleted ";
}
else{
tempShoe2->last = tempShoe1->last;
if(tempShoe1->last == NULL){
tempShoe2 = tempShoe2;
}
cout << "\nData deleted ";
}
delete(tempShoe1);
system("PAUSE");
MenuSportShoe();
}
else{
cout << "\nRecord not Found!!!" << endl;
system("PAUSE");
MenuSportShoe();
}
}
}
void SportShoe::ExitSportShoe(){
int sepatu;
cout << endl;
cout << "Please choose the option below."<<endl;
cout << ":: 1 :: Sport Shoe." << endl;
cout << ":: 2 :: Ladies High Heel." << endl;
cout << ":: 3 :: Exit" << endl;
cout << "=>> ";
cin >> sepatu;
while(sepatu == 1){
SportShoe listShoe;
listShoe.MenuSportShoe();
}
while(sepatu == 2){
HighHeel listShoe;
listShoe.MenuHighHeel();
}
while(sepatu == 3){
cout << "Thank you. Till we meet again."<< endl;
exit(1);
}
}
main() {
cout << "Hello! Welcome to MySepatu Online Shop administrator."<< endl;
cout << endl;
SportShoe::ExitSportShoe();
HighHeel::ExitHighHeel();
return 0;
}

Answer 4

public class linkedList {
int count = 0;
class Node {
int element;
Node next;
Node(int element) {
this.element = element;
}
}
Node head = null;
Node tail = null;
public void addNode(int Object) {
Node newNode = new Node(Object);
if (head == null) {
head = tail = newNode;
} else {
tail.next = newNode;
tail = newNode;
}
}
public void Display() {
Node current = head;
while (current!=null) {
System.out.println(current.element);
count ++;
current = current.next;
}
}
public void Length() {
System.out.println(count);
}
public void Remove(int node) {
Node curr = head;
while (curr!=null) { // looping the nodes
if (curr.element == node ) {
curr.element = curr.next.element;
curr = curr.next;
// To fix the Duplicates
while (curr!= tail) {
curr.element = curr.next.element;
curr = curr.next;
}
RemoveEnd();
break;
}
curr = curr.next;
}
}
public void RemoveEnd() {
Node current3 = head;
while (current3.next != tail) {
current3 = current3.next;
}
tail = current3;
tail.next = null;
}
}