Adding node in front of linklist - c++

I have implemented linklist as below,
struct node
{
int data;
node* next;
};
void initNode(node* head, int data)
{
head->data = data;
head->next = NULL;
}
void addNode(node* linkList, int data)
{
node* newnode = new node;
newnode->data = data;
newnode->next = NULL;
while (linkList)
{
if (linkList->next == NULL)
{
linkList->next = newnode;
return;
}
linkList = linkList->next;
}
}
void insertFrontNode(node* linkList, int data)
{
node* newnode = new node;
newnode->data = data;
newnode->next = linkList;
linkList = newnode;
}
void DisplayLinkList(struct node* linkList)
{
int i = 1;
while (linkList)
{
cout << "Linklist(" << i << ") " << linkList->data << endl;
linkList = linkList->next;
i++;
}
}
int main()
{
node* linkList =new node;
initNode(linkList, 5);
addNode(linkList, 10);
addNode(linkList, 30);
insertFrontNode(linkList, 12);
DisplayLinkList(linkList);
cin.get();
return 0;
}
My question is, when i initialise linklist in initNode or add node in addNode, the changes are reflected in linkst pointer which i am passing thru argument. but If i am adding node infront in insertFrontNode, changes are not reflecting in the linklist pointer.
Why? and what is difference?

You might find that adding a list (slist, single linked list) structure around your list will help (and make both add at head and add a tail O(1) operations).
struct node
{
int data;
node* next;
};
struct slist
{
node* head;
node* tail;
};
void addHead(slist* linkList, int data)
{
//new list node
node* newnode = new node;
newnode->data = data;
newnode->next = NULL;
newnode->next = linkList->head;
linklist->head = newnode->next;
}
void addTail(slist* list, int data)
{
//new list node
node* newnode = new node;
newnode->data = data;
newnode->next = NULL;
if( list->tail ) {
list->tail->next = newnode;
}
list->tail = newnode;
}
void DisplayLinkList(struct slist* linkList)
{
int i = 1;
node* link = linklist->head;
while (link)
{
cout << "Linklist(" << i << ") " << link->data << endl;
link = link->next;
i++;
}
}
int main()
{
slist* linkList=new slist;
addTail(linkList, 5);
addTail(linkList, 10);
addTail(linkList, 30);
addHead(linkList, 12);
DisplayLinkList(linkList);
return 0;
}

You are doing fine.You are modifying the head of your linked list but not updating it to your outer world.So when you are calling DisplayLinkList it is called with the old head pointer which is why the changes are not reflecting. Check the below code:
void insertFrontNode(node** linkList, int data)
{
node* newnode = new node;
newnode->data = data;
newnode->next = *linkList;
*linkList = newnode;
}
int main()
{
node* linkList = new node;
initNode(linkList, 5);
addNode(linkList, 10);
addNode(linkList, 30);
insertFrontNode(&linkList, 12);
DisplayLinkList(linkList);
cin.get();
return 0;
}
Above code,not only add the node at the front but also updates the head pointer such that display functions get the new updated head pointer.

Related

How Can I Create A Single function that can create multiple Linked Lists

as shown in the code , i have to use 2 similar functions for creating 2 linked lists . isn't there a way i can create as many lists as i want with just one function , i tried using struct Node **p and struct Node *p as a parameter to the function but the didn't work
can someone help me to create multiple linked lists using this same function
and i want to create a append function not a insert function which asks for position as well.
#include <iostream>
using namespace std;
struct Node
{
int data = 10 ;
struct Node *next;
} *first , *second , *third;
void Display(struct Node *p)
{
while (p)
{
cout<<p->data<<" ";
p = p->next ;
}
cout<<"\n";
}
void Append_1(int elem)
{
Node* t , *last;
t = new Node;
t->data = elem;
t->next = NULL;
if(first == 0)
first = last = t;
else
{
last->next = t;
last = t;
}
}
void Append_2(int elem)
{
Node* t , *last;
t = new Node;
t->data = elem;
t->next = NULL;
if(second == 0)
second = last = t;
else
{
last->next = t;
last = t;
}
}
//void SortMerge(struct Node *p , struct Node *q);
int main()
{
Append_1(3);
Append_1(7);
Display(first);
Append_2(10);
Append_2(14);
Append_2(21);
Display(second);
//SortMerge(first , second);
Display(third);
return 0;
}
You can create a class like here:
struct Node{
int data;
Node* next;
Node* previous;
};
class Graph{
public:
Graph(int = 0);
~Graph();
void display_left_right();
void display_right_left();
void append(int);
void append_at_pos(int,int);
void prepend(int);
int get_num_elt();
int get_data_at_pos(int);
private:
Node* head;
Node* tail;
int num_elt=0;
};
Graph::Graph(int first_data){
head = new Node;
head->next = NULL;
head->previous = NULL;
head->data = first_data;
tail = head;
num_elt++;
}
Graph::~Graph(){
Node* main_traverser = head;
while(main_traverser){
main_traverser = head->next;
delete head;
head = main_traverser;
}
std::cout <<"Graph deleted!" << std::endl;
}
void Graph::display_left_right(){
Node* traverser = head;
while(traverser != NULL){
std::cout << traverser->data << " ";
traverser = traverser->next;
}
std::cout << std::endl;
}
void Graph::display_right_left(){
Node* traverser = tail;
while(traverser != NULL){
std::cout << traverser->data << " ";
traverser = traverser->previous;
}
std::cout << std::endl;
}
void Graph::append(int new_data){
Node* add = new Node;
add->data = new_data;
add->next = NULL;
add->previous = tail;
tail->next = add;
tail = add;
num_elt++;
}
void Graph::append_at_pos(int pos, int new_data){
if(pos > num_elt+1 || pos<=0){std::cout << "Wrong position!" << std::endl; return;}
if(pos==1){
prepend(new_data);
return;
}
if(pos==num_elt+1){
append(new_data);
return;
}
Node* add = new Node;
Node* traverser = head;
add->data = new_data;
for(int i=0; i<pos-2; i++){
traverser = traverser->next;
}
add->next = traverser->next;
add->previous = traverser;
traverser->next->previous = add;
traverser->next = add;
}
void Graph::prepend(int new_data){
Node* add = new Node;
add->next = head;
add->previous = NULL;
add->data = new_data;
head->previous = add;
head = add;
num_elt++;
}
int Graph::get_num_elt(){
return num_elt;
}
int Graph::get_data_at_pos(int pos){
Node* traverser = head;
if(pos <=0 || pos> num_elt){std::cout << "Wrong position!" << std::endl; return 0;}
for(int i=0; i<pos-1; i++){
traverser = traverser->next;
}
return traverser->data;
}
main(){
Graph a(2);
a.append(3);
a.append(4);
a.prepend(1);
a.display_left_right();
a.append_at_pos(1,6);
a.display_left_right();
std::cout << "data at 1: " << a.get_data_at_pos(1) << std::endl;
}
When you say "create multiple linked lists," I think you mean creating nodes to a linked list, which you have 2 append functions. I think the reason you have these 2 functions is because you do not know where to start traversing your linked list. For this reason, I think in your main function you should declare the head of the linked list, a single node that is the start. Set it's data and next to null, and then pass the head value into a function so it can start traversing from the head. Here is a generic append function that adds a node on the end, where the parameters are a reference to the head node, and the value for the new node:
void append(Node ** head, int new_data)
{
Node * select_node = * head;
// select node is set to the head node, and will traverse until it is at the end
while (select_node -> next != NULL)
{
// select node is set to the next node until it is NULL (end of linked list)
select_node = select_node -> next;
}
// now that select node is the last node, we need to make it's next value a node
// and that node should be a new node (allocated in heap) with the value of the input value
//and the next value be NULL (because it's the end of the linked list)
Node * next_node = new Node();
next_node -> data = new_data;
next_node -> next = NULL;
select_node -> next = next_node;
}

Can any one tell what is the error in this Linked list creation

Inside insert function head is not updating.
#include<iostream>
#include<stdlib.h>
using namespace std;
struct node {
int data;
struct node* next;
}*head = NULL;
void insert(struct node* head, int data) {
struct node * newNode ;
newNode->data = data;
newNode->next = NULL;
if (head == NULL) {
head =newNode;
}
else {
struct node* current = head;
while (current->next != NULL) {
current = current->next;
}
//newNode->next = NULL;
current->next = newNode;
}
}
void display(struct node * head) {
struct node* current = head;
while (current) {
cout << current->data<<endl;
}
}
int main()
{
insert(head, 5);
insert(head, 6);
insert(head, 56);
insert(head, 65);
insert(head, 885);
insert(head, 66);
insert(head, 00);
display(head);
}
The problem with the code is your head outside the scope of your function is still NULL. You have to define a pointer to this head in order to update it. Apart from that it is required to dynamically allocate memory for the newNode.
void insert(struct node** head, int data) {
struct node * newNode = new node() ;
newNode->data = data;
newNode->next = NULL;
if (*head == NULL) {
*head = newNode;
}
else {
struct node* current = *head;
while (current->next != NULL) {
current = current->next;
}
//newNode->next = NULL;
current->next = newNode;
}
}
From main() call insert function as: insert(&head, 5);.
Another problem in your code is in display function, you're not updating current to current->next.
while (current) {
cout << current->data << endl;
current = current->next;
}

Linked List insertion isn't working in for/while loop

I am learning DSA, and was trying to implement linked list but the insertion function that i wrote is not
working in a for or while loop, its not the same when i call that function outside the loop, it works that way. I am not able to figure it out, please someone help me.
#include <iostream>
class Node {
public:
int data;
Node *next;
Node(int &num) {
this->data = num;
next = NULL;
}
};
class LinkedList {
Node *head = NULL;
public:
void insert(int num) {
Node *tmp;
if (head == NULL) {
head = new Node(num);
tmp = head;
} else {
tmp->next = new Node(num);
tmp = tmp->next;
}
}
void printList() {
Node *tmp = head;
while (tmp) {
std::cout << tmp->data << " ";
tmp = tmp->next;
}
std::cout << std::endl;
}
void reverseList() {
Node *curr = head, *prev = NULL, *nextNode;
while (curr) {
nextNode = curr->next;
curr->next = prev;
prev = curr;
curr = nextNode;
}
head = prev;
}
};
int main() {
LinkedList list1;
// This is not working
int num;
while (num != -1) {
std::cin >> num;
list1.insert(num);
}
// This is working
// list1.insert(1);
// list1.insert(2);
// list1.insert(3);
// list1.insert(4);
// list1.insert(5);
list1.printList();
list1.reverseList();
list1.printList();
return 0;
}
I expect this after insertion
Edit:
although #Roberto Montalti solved this for me, but before that I tried passing incrementing value using a for loop which worked but as soon as I pull that cin out it crashes. can someone tell me what's happening under the hood?
for (int i = 1; i <= 10; i++)
{
list1.insert(i);
}
When inserting the nth item (1st excluded) tmp is a null pointer, i don't understand what you are doing there, you are assigning to next of some memory then you make that pointer point to another location, losing the pointer next you assigned before, you must keep track of the last item if you want optimal insertion. This way you are only assigning to some *tmp then going out of scope loses all your data... The best way is to just keep a pointer to the last inserted item, no need to use *tmp.
class LinkedList
{
Node *head = NULL;
Node *tail = NULL;
public:
void insert(int num)
{
if (head == NULL)
{
head = new Node(num);
tail = head;
}
else
{
tail->next = new Node(num);
tail = tail->next;
}
}
...
}
You need to loop until you reach the end of the list and then add the new node after that. Like this.
void insert(int num) {
Node *tmp = head;
if (head == NULL) {
head = new Node(num);
}
else {
while (tmp->next != NULL) {
tmp = tmp->next;
}
tmp->next = new Node(num);
}
}
first of all you need to define a node for each of the tail and head of the list as follows
Node *h;
Node *t;
you may also separate the Node from the LinkedList class so you can modify easily
class Node{
public:
int data;
Node *next;
Node(int data, Node* next);
~Node();
};
Node::Node(int data, Node* next)
{
this->data= data;
this->next= next;
}
Node::~Node(){}
}
after that you can try to add these functions to your LinkedList class
so it can deal with other special cases such empty list or full, etc..
void addToHead(int data){
Node *x = new Node(data,h);
h=x;
if(t==NULL){
t=x;
}
void addToTail(int data){
Node *x = new Node(data,NULL);
if(isEmpty()){
h=t=x;
}
else
{
t->next=x;
t=x;
}
}
now for the insert function try this after you implemented the Node class and the other functions,
void insert(int v){
if(h==nullptr){addToHead(v); return;}
if(h->data>=v) {addToHead(v);return;}
if(t->data<=v) {addToTail(v); return;}
// In this case there is at least two nodes
Node *k=h->next;
Node *p=h;
while(k != nullptr){
if(k->data >v){
Node *z =new Node(v,k);
p->next=z;
return;
}
p=k;
k=k->next;
}
}
the idea of making all of this is not lose the pointer when it goes through elements in the Linked List so you don't end up with a run time error.
I hope this can be useful to you.
There was an issue with your insert function.
Read about segmentation fault here https://www.geeksforgeeks.org/core-dump-segmentation-fault-c-cpp/#:~:text=Core%20Dump%2FSegmentation%20fault%20is,is%20known%20as%20core%20dump.
for a quick workaround you can use this
using namespace std;
#include <iostream>
class Node
{
public:
int data;
Node *next;
Node(int num)
{
this->data = num;
next = NULL;
}
};
class LinkedList
{
Node *head = NULL;
public:
void insert(int num)
{
Node *tmp= new Node(num);
tmp->next=head;
head=tmp;
}
void printList()
{
Node *tmp = head;
while (tmp)
{
std::cout << tmp->data << " ";
tmp = tmp->next;
}
std::cout << std::endl;
}
void reverseList()
{
Node *curr = head, *prev = NULL, *nextNode;
while (curr)
{
nextNode = curr->next;
curr->next = prev;
prev = curr;
curr = nextNode;
}
head = prev;
}
};
int main()
{
LinkedList list1;
// This is not working
int num,i=0,n;
cout<<"Type the value of n";
cin>>n;
while (i<n)
{
cin >> num;
cout<<num<<" "<<&num<<endl;
list1.insert(num);
i++;
}
list1.printList();
list1.reverseList();
list1.printList();
return 0;
}

Linked List implementation of a Stack

Fairly new to implementing stacks and was looking for some possible feedback. My code gives the correct output, but I know this doesn't always mean it is working as it is suppose to. I chose to take the approach that implementing a stack using a linked list was essentially the same as your regular linked list implementation except that all the operations are done on the end of the list. I was not too sure if this approach was correct, but it followed the first in last out approach, and has the same complexity for access & search (O(n)) and insertion and deletion O(1). Such as pop() would just be deleting a node from the end of the linked list, and push() would just be appending a node to the end of the linked list. I have pasted my code below with comments within them explaining what I am doing or trying to do (if it is incorrect).
#include <iostream>
struct Node{
int data;
Node* next;
};
bool isEmpty(Node** stack){
if(*stack == NULL){
return true;
}
return false;
}
void push(Node** stack, int data){
Node* new_node = new Node();
new_node->data = data;
new_node->next=NULL;
// stack similar to "head"
if(isEmpty(&(*stack))){
*stack = new_node;
return;
}
Node* temp = *stack;
while(temp->next != NULL){
temp = temp->next;
}
temp->next = new_node;
}
void pop(Node** stack){
// checking if stack is empty
if(isEmpty(&(*stack))){
std::cout<<"Stack underflow"<<std::endl;
return;
}
Node* deleteMe = *stack;
// if at the first element in the stack
if(deleteMe->next == NULL){
*stack = (*stack)->next;
delete deleteMe;
return;
}
while(deleteMe->next != NULL){
if(deleteMe->next->next==NULL){
// saving the current location of the node before the node which I want to delete
Node* temp = deleteMe;
// updating the deleteMe pointer to the node which I want to delete
deleteMe = deleteMe->next;
// setting the current node before the deleteMe node to point to NULL instead of the node which I want to delete
temp->next = NULL;
delete deleteMe;
return;
}
deleteMe = deleteMe->next;
}
}
void printList(Node* stack){
Node* temp = stack;
while(temp!=NULL){
std::cout<<temp->data<<" ";
temp = temp->next;
}
std::cout<<"\n";
}
int top(Node** stack){
Node* top = *stack;
while(top->next!=NULL){
top = top->next;
}
return top->data;
}
int main(){
Node* stack = NULL;
// testing implementation below
push(&stack,10);
std::cout<<top(&stack)<<std::endl;
push(&stack,20);
std::cout<<top(&stack)<<std::endl;
push(&stack,30);
push(&stack,40);
printList(stack);
std::cout<<top(&stack)<<std::endl;
pop(&stack);
pop(&stack);
push(&stack,40);
std::cout<<top(&stack)<<std::endl;
}
Your implementation looks fine, one additional improvement can be done by maintaining head and tail pointer so that you can remove 1st and last element as needed. Here is example c++ code.
#include <iostream>
using namespace std;
template <class T> class node {
public:
node<T>() {}
~node<T>() {}
T data;
node<T> *next;
};
template <class T> class linked_list {
public:
linked_list<T>() : head(NULL), tail(NULL) {}
~linked_list<T>() {}
virtual void addFirst(T data) {
node<T> *n = new node<T>();
if (head == NULL)
tail = n;
n->data = data;
n->next = head;
head = n;
size++;
}
virtual void addLast(T data) {
node<T> *n = new node<T>();
n->data = data;
if (tail == NULL) {
head = n;
} else {
tail->next = n;
}
n->next = NULL;
tail = n;
}
virtual void reverse() {
if ((head == NULL) || (head->next == NULL))
return;
node<T> *current = head;
node<T> *previous = NULL;
node<T> *next = current->next;
tail = current;
while (current) {
next = current->next;
current->next = previous;
previous = current;
current = next;
}
head = previous;
}
virtual void print_nodes() {
node<T> *temp = head;
while (temp) {
cout << temp->data << " " << flush;
temp = temp->next;
}
cout << endl;
}
virtual void removeLast() {
node<T> *temp = head;
while (temp->next->next) {
temp = temp->next;
}
tail = temp;
delete temp->next;
temp->next = NULL;
}
virtual void removeFirst() {
node<T> *temp = head;
head = head->next;
delete temp;
}
private:
node<T> *head;
node<T> *tail;
uint32_t size;
};
int main(int argc, const char *argv[]) {
linked_list<uint32_t> *llist = new linked_list<uint32_t>();
llist->addLast(1);
llist->addFirst(5);
llist->addFirst(10);
llist->addFirst(15);
llist->addFirst(20);
llist->addLast(30);
llist->addFirst(40);
llist->print_nodes();
llist->reverse();
llist->print_nodes();
llist->removeLast();
llist->print_nodes();
llist->removeFirst();
llist->print_nodes();
return 0;
}

Simple linked list in C++

I am about to create a linked that can insert and display until now:
struct Node {
int x;
Node *next;
};
This is my initialisation function which only will be called for the first Node:
void initNode(struct Node *head, int n){
head->x = n;
head->next = NULL;
}
To add the Node, and I think the reason why my linked list isn't working correct is in this function:
void addNode(struct Node *head, int n){
struct Node *NewNode = new Node;
NewNode-> x = n;
NewNode -> next = head;
head = NewNode;
}
My main function:
int _tmain(int argc, _TCHAR* argv[])
{
struct Node *head = new Node;
initNode(head, 5);
addNode(head, 10);
addNode(head, 20);
return 0;
}
Let me run the program as I think it works. First I initialise the head Node as a Node like this:
head = [ 5 | NULL ]
Then I add a new node with n = 10 and pass head as my argument.
NewNode = [ x | next ] where next points at head. And then I change the place where head is pointing to NewNode, since NewNode is the first Node in LinkedList now.
Why isn't this working? I would appreciate any hints that could make me move in the right direction. I think LinkedList is a bit hard to understand.
When I'm printing this, it only returns 5:
This is the most simple example I can think of in this case and is not tested. Please consider that this uses some bad practices and does not go the way you normally would go with C++ (initialize lists, separation of declaration and definition, and so on). But that are topics I can't cover here.
#include <iostream>
using namespace std;
class LinkedList{
// Struct inside the class LinkedList
// This is one node which is not needed by the caller. It is just
// for internal work.
struct Node {
int x;
Node *next;
};
// public member
public:
// constructor
LinkedList(){
head = NULL; // set head to NULL
}
// destructor
~LinkedList(){
Node *next = head;
while(next) { // iterate over all elements
Node *deleteMe = next;
next = next->next; // save pointer to the next element
delete deleteMe; // delete the current entry
}
}
// This prepends a new value at the beginning of the list
void addValue(int val){
Node *n = new Node(); // create new Node
n->x = val; // set value
n->next = head; // make the node point to the next node.
// If the list is empty, this is NULL, so the end of the list --> OK
head = n; // last but not least, make the head point at the new node.
}
// returns the first element in the list and deletes the Node.
// caution, no error-checking here!
int popValue(){
Node *n = head;
int ret = n->x;
head = head->next;
delete n;
return ret;
}
// private member
private:
Node *head; // this is the private member variable. It is just a pointer to the first Node
};
int main() {
LinkedList list;
list.addValue(5);
list.addValue(10);
list.addValue(20);
cout << list.popValue() << endl;
cout << list.popValue() << endl;
cout << list.popValue() << endl;
// because there is no error checking in popValue(), the following
// is undefined behavior. Probably the program will crash, because
// there are no more values in the list.
// cout << list.popValue() << endl;
return 0;
}
I would strongly suggest you to read a little bit about C++ and Object oriented programming. A good starting point could be this: http://www.galileocomputing.de/1278?GPP=opoo
EDIT: added a pop function and some output. As you can see the program pushes 3 values 5, 10, 20 and afterwards pops them. The order is reversed afterwards because this list works in stack mode (LIFO, Last in First out)
You should take reference of a head pointer. Otherwise the pointer modification is not visible outside of the function.
void addNode(struct Node *&head, int n){
struct Node *NewNode = new Node;
NewNode-> x = n;
NewNode -> next = head;
head = NewNode;
}
I'll join the fray. It's been too long since I've written C. Besides, there's no complete examples here anyway. The OP's code is basically C, so I went ahead and made it work with GCC.
The problems were covered before; the next pointer wasn't being advanced. That was the crux of the issue.
I also took the opportunity to make a suggested edit; instead of having two funcitons to malloc, I put it in initNode() and then used initNode() to malloc both (malloc is "the C new" if you will). I changed initNode() to return a pointer.
#include <stdlib.h>
#include <stdio.h>
// required to be declared before self-referential definition
struct Node;
struct Node {
int x;
struct Node *next;
};
struct Node* initNode( int n){
struct Node *head = malloc(sizeof(struct Node));
head->x = n;
head->next = NULL;
return head;
}
void addNode(struct Node **head, int n){
struct Node *NewNode = initNode( n );
NewNode -> next = *head;
*head = NewNode;
}
int main(int argc, char* argv[])
{
struct Node* head = initNode(5);
addNode(&head,10);
addNode(&head,20);
struct Node* cur = head;
do {
printf("Node # %p : %i\n",(void*)cur, cur->x );
} while ( ( cur = cur->next ) != NULL );
}
compilation: gcc -o ll ll.c
output:
Node # 0x9e0050 : 20
Node # 0x9e0030 : 10
Node # 0x9e0010 : 5
Below is a sample linkedlist
#include <string>
#include <iostream>
using namespace std;
template<class T>
class Node
{
public:
Node();
Node(const T& item, Node<T>* ptrnext = NULL);
T value;
Node<T> * next;
};
template<class T>
Node<T>::Node()
{
value = NULL;
next = NULL;
}
template<class T>
Node<T>::Node(const T& item, Node<T>* ptrnext = NULL)
{
this->value = item;
this->next = ptrnext;
}
template<class T>
class LinkedListClass
{
private:
Node<T> * Front;
Node<T> * Rear;
int Count;
public:
LinkedListClass();
~LinkedListClass();
void InsertFront(const T Item);
void InsertRear(const T Item);
void PrintList();
};
template<class T>
LinkedListClass<T>::LinkedListClass()
{
Front = NULL;
Rear = NULL;
}
template<class T>
void LinkedListClass<T>::InsertFront(const T Item)
{
if (Front == NULL)
{
Front = new Node<T>();
Front->value = Item;
Front->next = NULL;
Rear = new Node<T>();
Rear = Front;
}
else
{
Node<T> * newNode = new Node<T>();
newNode->value = Item;
newNode->next = Front;
Front = newNode;
}
}
template<class T>
void LinkedListClass<T>::InsertRear(const T Item)
{
if (Rear == NULL)
{
Rear = new Node<T>();
Rear->value = Item;
Rear->next = NULL;
Front = new Node<T>();
Front = Rear;
}
else
{
Node<T> * newNode = new Node<T>();
newNode->value = Item;
Rear->next = newNode;
Rear = newNode;
}
}
template<class T>
void LinkedListClass<T>::PrintList()
{
Node<T> * temp = Front;
while (temp->next != NULL)
{
cout << " " << temp->value << "";
if (temp != NULL)
{
temp = (temp->next);
}
else
{
break;
}
}
}
int main()
{
LinkedListClass<int> * LList = new LinkedListClass<int>();
LList->InsertFront(40);
LList->InsertFront(30);
LList->InsertFront(20);
LList->InsertFront(10);
LList->InsertRear(50);
LList->InsertRear(60);
LList->InsertRear(70);
LList->PrintList();
}
Both functions are wrong. First of all function initNode has a confusing name. It should be named as for example initList and should not do the task of addNode. That is, it should not add a value to the list.
In fact, there is not any sense in function initNode, because the initialization of the list can be done when the head is defined:
Node *head = nullptr;
or
Node *head = NULL;
So you can exclude function initNode from your design of the list.
Also in your code there is no need to specify the elaborated type name for the structure Node that is to specify keyword struct before name Node.
Function addNode shall change the original value of head. In your function realization you change only the copy of head passed as argument to the function.
The function could look as:
void addNode(Node **head, int n)
{
Node *NewNode = new Node {n, *head};
*head = NewNode;
}
Or if your compiler does not support the new syntax of initialization then you could write
void addNode(Node **head, int n)
{
Node *NewNode = new Node;
NewNode->x = n;
NewNode->next = *head;
*head = NewNode;
}
Or instead of using a pointer to pointer you could use a reference to pointer to Node. For example,
void addNode(Node * &head, int n)
{
Node *NewNode = new Node {n, head};
head = NewNode;
}
Or you could return an updated head from the function:
Node * addNode(Node *head, int n)
{
Node *NewNode = new Node {n, head};
head = NewNode;
return head;
}
And in main write:
head = addNode(head, 5);
The addNode function needs to be able to change head. As it's written now simply changes the local variable head (a parameter).
Changing the code to
void addNode(struct Node *& head, int n){
...
}
would solve this problem because now the head parameter is passed by reference and the called function can mutate it.
head is defined inside the main as follows.
struct Node *head = new Node;
But you are changing the head in addNode() and initNode() functions only. The changes are not reflected back on the main.
Make the declaration of the head as global and do not pass it to functions.
The functions should be as follows.
void initNode(int n){
head->x = n;
head->next = NULL;
}
void addNode(int n){
struct Node *NewNode = new Node;
NewNode-> x = n;
NewNode->next = head;
head = NewNode;
}
I think that, to make sure the indeep linkage of each node in the list, the addNode method must be like this:
void addNode(struct node *head, int n) {
if (head->Next == NULL) {
struct node *NewNode = new node;
NewNode->value = n;
NewNode->Next = NULL;
head->Next = NewNode;
}
else
addNode(head->Next, n);
}
Use:
#include<iostream>
using namespace std;
struct Node
{
int num;
Node *next;
};
Node *head = NULL;
Node *tail = NULL;
void AddnodeAtbeggining(){
Node *temp = new Node;
cout << "Enter the item";
cin >> temp->num;
temp->next = NULL;
if (head == NULL)
{
head = temp;
tail = temp;
}
else
{
temp->next = head;
head = temp;
}
}
void addnodeAtend()
{
Node *temp = new Node;
cout << "Enter the item";
cin >> temp->num;
temp->next = NULL;
if (head == NULL){
head = temp;
tail = temp;
}
else{
tail->next = temp;
tail = temp;
}
}
void displayNode()
{
cout << "\nDisplay Function\n";
Node *temp = head;
for(Node *temp = head; temp != NULL; temp = temp->next)
cout << temp->num << ",";
}
void deleteNode ()
{
for (Node *temp = head; temp != NULL; temp = temp->next)
delete head;
}
int main ()
{
AddnodeAtbeggining();
addnodeAtend();
displayNode();
deleteNode();
displayNode();
}
In a code there is a mistake:
void deleteNode ()
{
for (Node * temp = head; temp! = NULL; temp = temp-> next)
delete head;
}
It is necessary so:
for (; head != NULL; )
{
Node *temp = head;
head = temp->next;
delete temp;
}
Here is my implementation.
#include <iostream>
using namespace std;
template< class T>
struct node{
T m_data;
node* m_next_node;
node(T t_data, node* t_node) :
m_data(t_data), m_next_node(t_node){}
~node(){
std::cout << "Address :" << this << " Destroyed" << std::endl;
}
};
template<class T>
class linked_list {
public:
node<T>* m_list;
linked_list(): m_list(nullptr){}
void add_node(T t_data) {
node<T>* _new_node = new node<T>(t_data, nullptr);
_new_node->m_next_node = m_list;
m_list = _new_node;
}
void populate_nodes(node<T>* t_node) {
if (t_node != nullptr) {
std::cout << "Data =" << t_node->m_data
<< ", Address =" << t_node->m_next_node
<< std::endl;
populate_nodes(t_node->m_next_node);
}
}
void delete_nodes(node<T>* t_node) {
if (t_node != nullptr) {
delete_nodes(t_node->m_next_node);
}
delete(t_node);
}
};
int main()
{
linked_list<float>* _ll = new linked_list<float>();
_ll->add_node(1.3);
_ll->add_node(5.5);
_ll->add_node(10.1);
_ll->add_node(123);
_ll->add_node(4.5);
_ll->add_node(23.6);
_ll->add_node(2);
_ll->populate_nodes(_ll->m_list);
_ll->delete_nodes(_ll->m_list);
delete(_ll);
return 0;
}
link list by using node class and linked list class
this is just an example not the complete functionality of linklist, append function and printing a linklist is explained in the code
code :
#include<iostream>
using namespace std;
Node class
class Node{
public:
int data;
Node* next=NULL;
Node(int data)
{
this->data=data;
}
};
link list class named as ll
class ll{
public:
Node* head;
ll(Node* node)
{
this->head=node;
}
void append(int data)
{
Node* temp=this->head;
while(temp->next!=NULL)
{
temp=temp->next;
}
Node* newnode= new Node(data);
// newnode->data=data;
temp->next=newnode;
}
void print_list()
{ cout<<endl<<"printing entire link list"<<endl;
Node* temp= this->head;
while(temp->next!=NULL)
{
cout<<temp->data<<endl;
temp=temp->next;
}
cout<<temp->data<<endl;;
}
};
main function
int main()
{
cout<<"hello this is an example of link list in cpp using classes"<<endl;
ll list1(new Node(1));
list1.append(2);
list1.append(3);
list1.print_list();
}
thanks ❤❤❤
screenshot https://i.stack.imgur.com/C2D9y.jpg