I am fairly new to programming and I am working on a project that involves shifting nodes. How can I get a node at a particular position denoted by user input and increase its value by one? To better explain:
here is my code...or my attempt:
#include <iostream>
struct Node {
int data;
struct Node* next;
};
class LinkedList {
private:
Node* head;
public:
LinkedList()
{
head = NULL;
}
void print()
{
Node* current = head;
if (head != nullptr)
{
do
{
std::cout << current->data << " ";
current = current->next;
}
while (current != head);
}
}
};
int main()
{
LinkedList link_one;
int nodes;
std::cout << "nodes ";
std::cin >> nodes;
for (int index = 0; index < nodes; index++){
link_one.print();
}
link_one.print();
std::cout << std::endl;
}
try traverse
actually there is no need to write a answer, but...I am a newcomer :)
your function place_node should add a parameter:
int place_node(int idx)
then...traverse from your head node for "idx" times, modify the value of current node, that's it.
here's the complete code for function place_node to achieve your goal:
int place_node(int idx) //no need to return
{
Node* current = head;
int count, index = 0;
for(int i=0;i<idx;++i) current = current->next;
current->data+=1;
return 1; // no need to return
}
Related
I typed 1234, but the list has 4,3,2,1 in it. I suspect the problem is getchar() itself, or a function in the class, but I have no way to find out.
The link class is responsible for some linked list operations, such as deletion, insertion, etc., while the node class is responsible for creating and assigning nodes.
The createlist class is responsible for the creation of the linked list, which is the main source of the problem. I wrote the debug statement in it, so you can run it and see the results for yourself
using namespace std;
class Node
{
public:
int data;
Node *next;
Node()
{
next = nullptr;
}
Node(int data)
{
this->data = data;
}
Node(const Node &temp)
{
this->data = temp.data;
}
};
class Link
{
public:
Node *head;
int length = 0;
Link()
{
head = new Node();
}
~Link()
{
while (head != nullptr)
{
Node *p = head->next;
free(head);
head = p;
}
}
void insert(const Node &cache)
{
Node *temp = new Node(cache);
temp->next = head->next;
head->next = temp;
length++;
}
};
void Creatlist(Link &link)
{
char cache;
while (1)
{
cache = getchar();
if (cache == '\n')
break;
link.insert(Node(cache - '0'));
cout << cache << " ";
}
cout<<endl;
Node *p = link.head->next;
cout << "in the linklist:";
while (p != nullptr)
{
cout << p->data << " ";
p = p->next;
}
}
int main()
{
Link link;
cout<<"inut numbers:"<<endl;
Creatlist(link);
}```
With the insert you inserted to the FRONT of the list. So you had "1", then "2->1" ... If you want to insert to the end, don't insert at the head, but hake a Node* tail in the class Link and an insert_end function as
//...
Node* temp;
void insert_end(const Node &cache){
Node *temp = new Node(cache);
tail->next=temp;
tail=tail->next;
length++;
}
Alsoin the constructor set tail=head
I am trying to implement a simple open hash in c++ for the sake of learning. I am getting very confused about the interaction of functions with array pointers, and I am at the end of my wits.
The code:
struct node{
int data;
node* next;
node* prev;
bool state;
node(){
prev = next = NULL;
state = true;
}
};
//state true means empty, state false means full.
void insert(node *array,int value){
node *current = array;
if(array->state == true){
array->data = value;
array->state = false;
} else {
node* add = new node();
add->data = value;
add->state = false;
while(current->next != NULL){
current = current->next;
}
current->next = add;
add->prev = current;
}
}
void display(node *array, int size){
node *show = new node();
for(int i = 0; i< size; i++){
if(array->state == false){
cout<<array->data;
show = array;
while(show->next != NULL){
show = show->next;
cout<<" --> "<<show->data;
}
} else {
cout<<"Empty.";
}
cout<<"\n\n";
}
}
int main(){
int size;
cout<<"Enter size of the hash table: ";
cin>>size;
node *array = new node[size];
int value;
cout<<"Enter Value: ";
cin>>value;
int index = value%size;
//inserting single value
insert(&array[index],value);
//Hash table output.
display(array,size);
return 0;
}
When I run this code, instead of showing "empty" in places where the array's state is empty, it seems as if the entire array has the same value. The problem lies in the insert function, but I cannot figure it out.
You can simplify this by making the Hashtable an array of pointers to Node. A nullptr then means the slot is empty and you don't have empty and full nodes. Also Nodes only need a next pointer and usually new entries are added to the beginning of the buckets instead of the end (allows duplicate entries to "replace" older ones). Inserting at the beginning of a list becomes real easy with Node **.
#include <cstddef>
#include <iostream>
struct Table {
struct Node {
Node * next;
int data;
Node(Node **prev, int data_) : next{*prev}, data{data_} {
*prev = this;
}
};
std::size_t size;
Node **tbl;
Table(std::size_t size_) : size{size_}, tbl{new Node*[size]} { }
~Table() {
for (std::size_t i = 0; i < size; ++i) {
Node *p = tbl[i];
while(p) {
Node *t = p->next;
delete p;
p = t;
}
}
delete[] tbl;
}
void insert(int value) {
Node **slot = &tbl[value % size];
new Node(slot, value);
}
void display() const {
for(std::size_t i = 0; i < size; i++) {
std::cout << "Slot " << i << ":";
for (const Node *node = tbl[i]; node; node = node->next) {
std::cout << " " << node->data;
}
std::cout << std::endl;
}
}
};
int main(){
std::size_t size;
std::cout << "Enter size of the hash table: ";
std::cin >> size;
Table table{size};
int value;
std::cout << "Enter Value: ";
std::cin >> value;
//inserting single value
table.insert(value);
//Hash table output.
table.display();
return 0;
}
Whats wrong with this code?
I am writing this code to implement singly linked list using arrays but its not working. Im using code::blocks and its crashing on run time. Please help.
I must have missed out on something when it was taught in the class. xD
#include<iostream>
#include<stdio.h>
using namespace std;
class Node
{
int data;
Node *next;
public:
Node(int n)
{
data=n;
next=NULL;
}
friend class List;
};
class List
{
Node *listptr;
public:
void create();
void display();
};
void List::create()
{
Node *temp;
int n, num;
cout << "Enter number of nodes:" << endl;
cin >> n;
cout << "/nEnter the data" << endl;
for(int i=0; i<n; i++)
{
cin >> num;
Node *new_node=new Node(num);
if(listptr==NULL)
listptr=temp=new_node;
else
{
temp->next=new_node;
temp=temp->next;
}
}
}
void List::display()
{
Node *temp=listptr;
while(temp!=NULL)
{
cout << temp->data << "->";
temp=temp->next;
}
}
main()
{
List l1;
l1.create();
l1.display();
}
listptr not initialized, you can initialize in constructor.
List() {
listptr = 0;
}
Class List should be
class List
{
Node *listptr;
public:
List() {
listptr = 0;
}
void create();
void display();
};
Try following piece of code -
First Creating Node
class ListElement
{
int data;
ListElement* next;
public:
void set_element(int item) { data = item; }
int get_value() { return data; }
friend class List;
};
Another class for further operation
class List
{
ListElement *Start, *Tail, *New;
public:
List() { Start = Tail = New = NULL; } // initialise all pointer value to NULL
void add_element(int element) {
// Create a new Node
New = new ListElement;
New->set_element(element);
New->next = NULL;
// adding value or linkig each node to each other
(Start == NULL) ? Start = New : Tail->next = New;
Tail = New;
}
// print the whole linked list
void print()
{
ListElement* Current = Start;
while (Current != NULL)
{
cout << Current->get_value() << endl;
Current = Current->next;
}
}
};
Main Function
int main()
{
List L;
int num_of_element, element;
cin >> num_of_element;
for (int i(0); i < num_of_element; i++) {
cin >> element;
L.add_element(element);
}
L.print();
}
Hope it'll work.
I didn't put the full code because it was very long and i only need help with the small portion which is the **** area. i can't seem to use front() or top() to get the top element of the queue. I tried making top() function List keep getting error : 1) class List has no memeber named 'top' which means i don't have a function top in List, when i make it it says 2) no match for 'operator=' in printer_cpu[i] = SList::top() with T=PCB]()'
template <class T>
class node{
public:
T data;
node *next;
};
template <class T>
class List{
node<T> *head;
node<T> *tail;
public:
List()
{
head = tail = NULL;
}
bool isEmpty()
{
if(head == NULL) return true;
else return false;
}
void enqueue(T new_data){
node<T> *temp = new node<T>;
temp->data = new_data;
temp->next = NULL;
if(isEmpty()){
head = temp;
tail = temp;
}
else{
tail->next = temp;
tail = temp;
}
}
void dequeue(){
if(isEmpty())
{
cout << "The list is already empty" << endl;
}
node<T>* temp;
if(head == tail){
temp->data=head->data;
delete head;
head = tail = NULL;
}
else{
temp->data = head->data;
head = head->next;
delete temp;
}
}
node<T> top() // need help here ****
{
return head;
}
void display(){
node<T> *current = head;
while(current != NULL){
cout << current->data << endl;
current = current->next;
}
}
};
struct PCB
{
int ProcessID;
int ProcessorSize;
int priority;
string name;
};
typedef List<PCB> printing;
typedef List<PCB> disk;
void gen(vector<printing> &printer_queue,string printer_name[], int printers)
{
for(int i = 0; i < printers; i++)
{
int num = i+1;
ostringstream convert;
convert << num;
printer_name[i] = "p" + convert.str();
printer_queue.push_back(printing());
}
int main()
{
int numOfPrinter = 5;
string interrupt;
cin >> interrupt;
PCB cpu;
PCB printer_cpu[numOfPrinter];
string printer_name[numOfPrinter];
vector<printing> PQ;
gen(PQ,printer_name,numOfPrinter);
for(int i = 0; i < numOfPrinter; i++)
{
if(interrupt == printer_name[i])
{
cout << "Enter a name for this printer file: " << endl;
cin >> cpu.name;
PQ[i].enqueue(cpu);
printer_cpu[i] = PQ[i].top(); //need help here ****
}
}
}
It looks like you're missing an asterisk, because you need to return of type pointer, because that's what head is.
You should have
node<T> * top()
{
...
}
You also need to overload the = operator, because you are trying to compare type PCB with type node *.
Well, I compile your code successfully after correcting some mistakes.
I didn't meet class List has no memeber named 'top' problem.
Then your top() function returns the value of head, so you should change it to: node<T>* top() because head is a pointer to node<T>.
And the reason you got no match for 'operator=' error is that printer_cpu[i]'s type is PCB while PQ[i].top()'s type should be node<T>*
I have also found that the code you post lacks a } just before int main().
I got a problem with my doubly linked list. How can i make the input unique ( i don`t want it to be repeated )
for example i can input 1 and then again 1 i will have a list of 1 and 1. I need to forbid this somehow :) so the list can contain only not repeating numbers.
#include <cstdlib>
#include <iostream>
using namespace std;
struct node
{
int data;
node* next;
node* prev;
};
class Node
{
public:
Node();
~Node();
void setKopa();
void printForward();
private:
node* head;
node* tail;
node* n;
};
Node::Node()
{
setKopa();
}
Node::~Node()
{
delete n;
}
void Node::setKopa()
{
int lenght;
do
{
cout << "Input list lenght (how many elements): ";
cin >> lenght;
if(lenght<2)
cout << "Error list has to have atleast 2 elements!" <<endl;
}
while(lenght<2);
int fill;
cout << "Input "<< lenght <<" elements: "<<endl;
for (int i=0; i<lenght; i++)
{
cin>>fill;
n = new node;
n->data = fill;
if (i==0)
{
n->prev = NULL;
head = n;
tail = n;
}
else if (i+1==lenght)
{
n->prev = tail;
tail->next = n;
tail = n;
tail->next = NULL;
}
else
{
n->prev = tail;
tail->next = n;
tail = n;
}
}
}
void Node::printForward()
{
node* temp = head;
while(temp != NULL)
{
cout << temp->data << " ";
temp = temp-> next;
}
cout << endl;
}
int main()
{
Node a;
a.printForward();
system("pause");
return 0;
}
When you read input, go through the list to see if the input is already there.
With that (simple) answer out of the way, I would like to address some other things regarding your code. The first is that you have a memory leak in that you never delete the list. The second is that you don't need the class member variable n, it might as well be a local variable inside the setKopa loop.
Your way of adding new nodes is also, well, weird. It should, in my opinion, be more general instead of using the loop counter to check what to do. What I suggest is that you make a member function to add new nodes, taking the integer data as argument. This way you can call this function to add nodes anywhere, and not just in the setKopa function. In fact, I think the list should not handle that input at all, instead it should be a free-standing function called from main and which calls the addNode function.
Also the node structure doesn't need to be in the global namespace, it could be a private structure in the Node class. And speaking of the Node class, shouldn't it really be called List instead?
So if I may suggest, you might want to do something like this:
#include <iostream>
class List
{
public:
List()
: head(nullptr), tail(nullptr)
{}
~List();
void addNode(const int data);
void printAll() const;
private:
struct node
{
node()
: next(nullptr), prev(nullptr)
{}
node* next;
node* prev;
int data;
};
node* head;
node* tail;
};
List::~List()
{
for (node* next, *cur = head; cur; cur = next)
{
next = cur->next;
delete cur;
}
}
void List::addNode(const int data)
{
node* n = new node;
n->data = data;
if (tail == nullptr)
{
// First node in list
head = tail = n;
}
else
{
n->prev = tail;
tail->next = n;
tail = n;
}
}
void List::printAll() const
{
std::cout << "{ ";
for (node* cur = head; cur != nullptr; cur = cur->next)
std::cout << cur->data << ' ';
std::cout << "}\n";
}
int main()
{
List list;
for (int i = 0; i < 10; ++i)
list.addNode(i);
list.printAll();
}
The above code should print
{ 0 1 2 3 4 5 6 7 8 9 }
Replace the node-adding loop with your own.