when i run this program, it gives me a segmentation fault after runs the printlist function. I'm not sure why the program is completely skipping over the input function. I set the input variable to a number in the function already so it couldn't be some left over value causing it right?
class function implementation:
#include <iostream>
#include "OrderedList.h"
using namespace std;
OrderedList::OrderedList() {
head = nullptr;
}
OrderedList::OrderedList(const OrderedList& a) {
ListNode * newNode;
ListNode * copyNode;
if(!a.head){
return;
}else {
copyNode = a.head;
newNode = new ListNode;
this->head = newNode;
head->value = copyNode->value;
copyNode = copyNode->next;
newNode->next = nullptr;
}
}
OrderedList :: ~OrderedList() {
ListNode * nodePtr;
ListNode * nextNode;
nodePtr = head;
while(nodePtr != nullptr){
nextNode = nodePtr->next;
delete nodePtr;
nodePtr = nextNode;
}
}
void OrderedList :: insert() {
int num = 0;
while(num){
cout << "Type a number for insertion (type x to stop): ";
cin >> num;
ListNode * newNode;
ListNode * prev;
ListNode * nodePtr;
newNode = new ListNode;
newNode->value = num;
newNode->next = nullptr;
if(!head){
head = newNode;
newNode->next = nullptr;
}else {
nodePtr = head;
prev = nullptr;
while(nodePtr != nullptr && nodePtr->value < num){
prev = nodePtr;
nodePtr = nodePtr->next;
}
if(prev == nullptr){
head = newNode;
newNode->next = nodePtr;
}else {
prev->next = newNode;
newNode->next = nodePtr;
}
}
}
}
void OrderedList :: printList() {
ListNode * nodePtr;
nodePtr = head;
while(nodePtr != nullptr){
cout << nodePtr->value << " ";
nodePtr = nodePtr->next;
}
cout << endl;
}
driver program:
#include <iostream>
#include <iomanip>
#include "OrderedList.h"
using namespace std;
int main() {
OrderedList A;
cout << "Asking user to type and create listA..." << endl;
A.insert();
cout << "listA is: " << setw(20) << endl;
A.printList();
OrderedList B(A);
cout << "listB is copied from listA: ";
B.printList();
}
the output looks like this by the way:
Asking user to type and create listA...
listA is:
Segmentation fault (core dumped)
Related
Compiles fine but when executed I get segmentation fault (core dumped) error. I've tested each function individually and the add function is the only one giving me this error. Add function is supposed to add the value to the head of the linked list. When running the code, values get added to the list correctly and I can display the list, but the error follows shortly after.
//Homework 11
//Linked List
#include <iostream>
using namespace std;
//Declaring class and Linked List.
class NumberList
{
private:
struct ListNode
{
double value;
struct ListNode *next;
};
ListNode *head;
public:
NumberList()
{ head = NULL;}
~NumberList()
{
ListNode *nodePtr;
ListNode *nextNode;
nodePtr = head;
while (nodePtr != NULL)
{
nextNode = nodePtr->next;
delete nodePtr;
nodePtr = nextNode;
}
}
//Function inserting node at the head.
void add(double x)
{
ListNode *newNode;
ListNode *nodePtr;
ListNode *previousNode = NULL;
newNode = new ListNode;
newNode->value = x;
if (!head)
{
head = newNode;
newNode -> next = NULL;
}
else
{
nodePtr = head;
previousNode = NULL;
}
if (previousNode == NULL)
{
head = newNode;
newNode->next = nodePtr;
}
}
//Function to find matching values.
bool isMember(double x)
{
int pos = 0;
bool flag = false;
if (head == NULL)
{
cout << "List is Empty" << endl;
return flag;
}
ListNode *nodePtr;
nodePtr = head;
while (nodePtr != NULL)
{
pos++;
if (nodePtr->value == x)
{
flag = true;
cout << x << " was found at position " << pos << endl;
}
nodePtr = nodePtr->next;
}
if (!flag)
{
cout << x << " not found in the list." << endl;
}
return flag;
}
//Function to display linked list values.
void display() const
{
ListNode *nodePtr;
if (head == NULL)
{
cout << "List is empty." << endl;
return;
}
nodePtr = head;
cout << "The list goes: " << endl;
while (nodePtr != NULL)
{
cout << nodePtr->value << endl;
nodePtr = nodePtr->next;
}
cout << "End" << endl;
}
//Function to delete a selected value in the list.
void deletNodeAll(double x1)
{
ListNode *nodePtr;
ListNode *previousNode;
if (!head)
return;
if (head->value == x1)
{
nodePtr = head->next;
delete head;
head = nodePtr;
}
else
{
nodePtr = head;
while ( nodePtr != NULL && nodePtr->value != x1)
{
previousNode = nodePtr;
nodePtr = nodePtr->next;
}
if (nodePtr)
{
previousNode->next = nodePtr->next;
delete nodePtr;
}
}
}
};
int main()
{
NumberList Z;
Z.add(3);
Z.add(4);
Z.add(2);
Z.add(5);
Z.add(7);
Z.add(4);
Z.add(7);
Z.add(5);
Z.add(2);
Z.display();
Z.isMember(2);
Z.deletNodeAll(2);
Z.display();
return 0;
}
your add() method causes segmentation fault because for first node you should update the head and head->next and return but you didn't.
if (!head) {
head = newNode;
newNode -> next = NULL;
return ;/* do this else this again check previousNode == NULL also
which is not needed 1st time */
}
Also deletNodeAll() deletes only first occurrence of number you are passing, there is a bug in logic,check it yourself.
I don't know why PrintList() doesn't terminate. It is a LinkedList, so when I go to next, that should terminate.
When I do AddNode once and then print, that terminates, when I do addNode twice, print doesn't terminate.
The reason why in constructor I create 5 empty spots is because I'm required to create those 5 empty spots when program starts.
Moreover, if for example I add twice , how I can assign pointer to that second value?
#pragma once
class LinkedList
{
private:
typedef struct node {
int data;
node* next;
}* nodePtr;
nodePtr n;
nodePtr head;
nodePtr curr;
nodePtr temp;
public:
LinkedList();
void AddNode(int addData);
void PrintList();
~LinkedList();
};
#include "LinkedList.h"
#include<cstdlib>
#include<iostream>
using namespace std;
LinkedList::LinkedList()
{
head = NULL;
curr = NULL;
temp = NULL;
n = new node;
for (int x = 1; x <= 5; x++) {
//cout << n<<endl;
n->next = n;
}
}
void LinkedList::AddNode(int addData) {
//nodePtr n = new node;
n->next = NULL;
n->data = addData;
cout << n <<endl;
if (head != NULL) {
curr = head;
while (curr->next != NULL) {
curr = curr->next;
}
curr->next = n;
}
else {
head = n;
}
}
void LinkedList::PrintList() {
curr = head;
while (curr != NULL) {
cout << curr->data << endl;
curr = curr->next;
}
}
LinkedList::~LinkedList()
{
head = NULL;
curr = NULL;
temp = NULL;
delete n;
}
#include <iostream>
#include <fstream>
#include <string>
#include <cstdlib>
#include "LinkedList.h"
using namespace std;
int main() {
LinkedList *l = new LinkedList();
l->AddNode(5);
l->AddNode(8);
l->PrintList();
system("pause");
return 0;
}
The node n is always the same since you are not setting n to a different node
So when you do n->next and n->data , the same node is being modified each time
void LinkedList::AddNode(int addData) {
//nodePtr n = new node; // you need to uncomment this
n->next = NULL;
n->data = addData;
cout << n <<endl;
if (head != NULL) {
curr = head;
while (curr->next != NULL) {
curr = curr->next;
}
curr->next = n;
}
else {
head = n;
}
}
After your first addNode(5), lets examine the values.
head = n
head->data = 5
head->next = null
After your second addNode(8)
head = n
head->data = 8
head->next = n // set by "curr->next = n" .
So you have a problem here. When you try to loop through your linked list, it will become head->next->head->next->head->next->head->next ..... causing an infinite loop
I am trying to display a doubly linked list backwards, but every time I try to run anything even remotely touching the "prev" pointer in the program I get a seg fault.
I've been trying to figure this out for about 4 hours now and I just can't seem to pin it down. I can't tell if the issue is coming from my print backwards function or from the actual prev pointers themselves.
#include <iostream>
#include "list.h"
LinkedList::LinkedList(){
head = NULL;
tail = NULL;
};
bool LinkedList::addAtBeginning(int val){
Node *upd8L = head; // This Node will update Last
Node *upd8 = head;; // This Node will update the previous pointers
Node *point = new Node(); // This Node will insert the new node at the beginning
point->data=val; // This sets the data in the new node
point->next=head; // This sets the next pointer to the same as head
head = point; // This sets the head to the new Node
while(upd8){
upd8 = upd8->next;
upd8->prev = upd8L;
upd8L=upd8L->next;
}
return true;
};
bool LinkedList::remove(int val){
Node *temp = head;
Node *trail = 0;
while(temp != NULL){
if(temp->data == val){
if(temp->next == head->next){
head = head->next;
}else{
trail->next = temp->next;
}
delete temp;
}
trail = temp;
temp = temp->next;
}
return true;
};
void LinkedList::printForward() const{
Node *temp;
temp = head;
while(temp){
cout << temp -> data << endl;
temp = temp->next;
}
};
void LinkedList::printBackward() const{
Node *temp = head;
while(temp){
temp = temp->next;
cout << temp->data << endl;
}
while(temp){
cout << temp->data;
cout << "Pop" << endl;
temp = temp-> prev;
}
};
If possible, I'd love an explanation as to what is bugging up my program rather than just a straight answer, I want to know what I'm doing wrong and why it's wrong.
Thank you!
edit
Here's list.h
#ifndef LIST_H
#define LIST_H
#include <iostream>
using namespace std;
class LinkedList
{
private:
struct Node
{
int data;
Node * next;
Node * prev;
};
Node * head, * tail;
public:
LinkedList();
bool addAtBeginning(int val);
bool remove(int val);
void printForward() const;
void printBackward() const;
};
#endif
The function printBackward() may cause a seg-fault in the last iteration of the loop. while(temp) means iterate till you get the element out of the list NULL. Then you assigning temp = temp->next where temp->next is NULL. Now when you are calling cout << temp->data << endl; you are trying to get data from NULL pointer. Try to change the order. First display the node data, then change the temp pointer. An example:
void LinkedList::printBackward() const{
Node *temp = head;
while(temp){
cout << temp->data << endl;
temp = temp->next;
}
What you are doing wrong is getting the data from a NULL pointer.
So, I figured it out after a ton of trial and error!
The biggest issue I was having that kept giving me segmentation errors was whenever I was removing elements of the list I was failing to update the "prev" part of the node, and as a result any time I tried to read the list backwards I was getting a seg error.
//put your implementation of LinkedList class here
#include <iostream>
#include "list.h"
LinkedList::LinkedList(){
head = NULL;
tail = NULL;
};
bool LinkedList::addAtBeginning(int val){
Node *point = new Node(); // This Node will insert the new node at the beginning
point->data=val; // This sets the data in the new node
point->next=head; // This sets the next pointer to the same as head
head = point; // This sets the head to the new Node
if(head->next != NULL){
Node *temp = head->next;
temp->prev = head;
}
return true;
};
bool LinkedList::remove(int val){
Node *temp = head->next;
Node *trail = head;
if(head->data ==val){
head = head->next;
head->prev = NULL;
delete trail;
}else{
while(temp != NULL){
if(temp->data == val){
if(temp->next != NULL){
trail->next = temp->next;
delete temp;
temp= temp->next;
temp->prev=trail;
}else{delete temp;
trail->next = NULL;
}
}
trail = temp;
temp = temp->next;
}
}
return true;
};
void LinkedList::printForward() const{
Node *temp;
temp = head;
while(temp){
cout << temp->data << endl;
temp = temp->next;
}
};
void LinkedList::printBackward() const{
Node *temp = head;
while(temp->next != NULL){
temp = temp->next;
}
while(temp->prev != NULL){
cout << temp->data << endl;
temp = temp->prev;
}
cout << head->data << endl;
};
When I run my program, it works as intended, except the items in the list have no spaces between them when the displayList() function is called. I have 3 files. The main cpp file is ShoppingList.cpp. Then I have two other files for the linked list classification and implementation.
//ShoppingList.cpp
//Michael Hery
//COP 2001
//11/9/17
//Shopping List
#include <iostream>
#include <string>
#include "strList.h"
#include "strlist.cpp"
using namespace std;
int main()
{
//Define a NumberList object
StrList list;
string item;
string delItem;
int menuSelection;
//Ask the user how many items to
//put in the list
cout << "How many items would you like to put it the list? >> ";
cin >> menuSelection;
while (menuSelection < 1)
{
cout << "Please enter a valid number (greater than 0) >> ";
cin >> menuSelection;
}
for (int i = 0; i < menuSelection; i++)
{
cout << "Please enter item " << i + 1 << ": ";
cin >> item;
list.appendNode(item);
}
list.displayList();
cout << "Which item do you wish to delete from the list? >> ";
cin >> delItem;
while (delItem == "")
{
cout << "Please enter a valid item >> ";
cin >> delItem;
}
list.deleteNode(delItem);
list.displayList();
//Wait for user input to exit program
system("PAUSE");
return 0;
}
//strList.h
#ifndef STRLIST_H
#define STRLIST_H
#include <iostream>
#include <string>
namespace
{
class StrList
{
private:
struct ListNode
{
std::string value;
struct ListNode *next;
};
ListNode *head;
public:
//Constructor
StrList()
{
head = nullptr;
}
//Destructor
~StrList();
//Linked List Operations
void appendNode(std::string item);
void insertNode(std::string item);
void deleteNode(std::string item);
void displayList() const;
};
}
#endif
//strList.cpp
#ifndef STRLIST_CPP
#define STRLIST_CPP
#include <iostream>
#include <string>
#include "strList.h"
void StrList::appendNode(std::string item)
{
ListNode *newNode;
ListNode *nodePtr;
//Allocate a new node and store item there
newNode = new ListNode;
newNode->value = item;
newNode->next = nullptr;
//If there are no nodes in the list
//make newNode the first node
if (!head)
head = newNode;
else //Otherwise, insert newNode at the end
{
//Initialize nodePtr to head of the list
nodePtr = head;
//Find the last node in the list
while (nodePtr->next)
nodePtr = nodePtr->next;
//Insert newNode as the last node
nodePtr->next = newNode;
}
}
void StrList::insertNode(std::string item)
{
ListNode *newNode;
ListNode *nodePtr;
ListNode *previousNode = nullptr;
//Allocate a new node and store num there
newNode = new ListNode;
newNode->value = item;
//If there are no nodes in the list
//make newNode the first node
if (!head)
{
head = newNode;
newNode->next = nullptr;
}
else //Otherwise, insert newNode
{
//Position nodePtr at the head of list
nodePtr = head;
//Initialize previousNode to nullPtr
previousNode = nullptr;
//Skip all nodes whose values is less than num
while (nodePtr != nullptr && nodePtr->value < item)
{
previousNode = nodePtr;
nodePtr = nodePtr->next;
}
//If the new node is to be the 1st in the list,
//insert it before all the other nodes
if (previousNode == nullptr)
{
head = newNode;
newNode->next = nodePtr;
}
else //Otherwise insert after the previous node
{
previousNode->next = newNode;
newNode->next = nodePtr;
}
}
}
void StrList::deleteNode(std::string item)
{
ListNode *nodePtr; //To traverse the list
ListNode *previousNode = nullptr; //To point to the previous node
//If the list is empty, do nothing
if (!head)
return;
//Determine if the first node is the one
if (head->value == item)
{
nodePtr = head->next;
delete head;
head = nodePtr;
}
else
{
//Initialize nodePtr to head of list
nodePtr = head;
//Skip all nodes whose value member is
//not equal to num
while (nodePtr != nullptr && nodePtr->value != item)
{
previousNode = nodePtr;
nodePtr = nodePtr->next;
}
//If nodePtr is not at the end of the list,
//link the previous node to the node after
//nodePtr, then delete nodePtr
if (nodePtr)
{
previousNode->next = nodePtr->next;
delete nodePtr;
}
}
}
StrList::~StrList()
{
ListNode *nodePtr; //To traverse the list
ListNode *nextNode; //To point to the next node
//Position nodePtr at the head of the list
nodePtr = head;
//While nodePtr is not at the end of the list
while (nodePtr != nullptr)
{
//Save a pointer to the next node
nextNode = nodePtr->next;
//Delete the current node
delete nodePtr;
//Position nodePtr at the next node
nodePtr = nextNode;
}
}
void StrList::displayList() const
{
ListNode *display;
display = head;
std::cout << "**********************************" << std::endl;
std::cout << "**** Your Shopping List ****" << std::endl;
std::cout << "**********************************" << std::endl;
while (display)
{
std::cout << display->value;
display = display->next;
}
}
#endif
The problem lies in the displayList(); function towards the end of the file.
Add a separator for between your values.
char const* sep = "";
while (display)
{
std::cout << sep << display->value;
sep = " ";
display = display->next;
}
i am in a bit of a stand still with my program on adding a newnode to a linked it, its supposed to be added at the end of the list but i tried all i could but still having got a solution, was hoping if any of you guys could help me with it
Thanks in advance tho;
this is the bit of code
#include <iostream>
using namespace std;
struct node {
int data;
node* next;
};
node* head;
void insert(int x);
void numInsert();
void numSearch();
int main()
{
head=NULL;
int x,n;
cout <<"How many number? \n";
cin >>n;
for (int i=0; i<n; i++){
cout <<"Enter Number \n";
cin >> x;
}
node* newNode;
newNode = new node();
newNode->data=x;
newNode->next=head;
head=newNode;
/*
NewNode->next=NULL;
if (head !=NULL){
NewNode->next=head;
}
else{
head=NewNode;
}*/
int num;
cout<<"what number do you want to insert in the list \n";
cin>>num;
node *nNode;
nNode = new node();
nNode->data=num;
nNode->next=NULL;
node *prevNode;
node *currNode;
prevNode=NULL;
currNode=NULL;
{
node* nNode= new node;
nNode->data= num;
nNode->next= NULL;
currNode=NULL; prevNode=NULL;
for(currNode=head; currNode != NULL; currNode= currNode->next)
{
if (newNode->data <= currNode->data)
{
break;
}
prevNode = currNode;
}
newNode->next=prevNode->next;
prevNode->next=newNode;
}
return 0;
}
anytime i run it , gets to a point and just stops working , pls help me out, the assignment is due today and i have no clue on how to solve it properly
#include <iostream>
using namespace std;
struct node {
int data;
node* next;
};
node* head;
node* tail;
void insert(int x);
void numInsert();
void numSearch();
int main()
{
head=NULL;
tail = NULL;
int x,n;
cout <<"How many number? \n";
cin >>n;
for (int i=0; i<n; i++){
cout <<"Enter Number \n";
cin >> x;
if(head==NULL){
head = new node();
head->data = x;
head->next = NULL;
tail = head;
}else{
node* newNode;
newNode = new node();
newNode->data=x;
newNode->next = NULL;
tail->next = newNode;
tail = tail->next;
}
}
cout << "Linked List :" << "\n";
node* trav = head;
for (int i=0; i<n; i++){
cout << (trav->data) << '\n';
trav = trav->next;
}
int num;
cout<<"what number do you want to insert in the list \n";
cin>>num;
if(head==NULL){
head = new node();
head->data = num;
head->next = NULL;
tail = head;
}else{
node* newNode;
newNode = new node();
newNode->data=num;
newNode->next = NULL;
tail->next = newNode;
tail = tail->next;
}
cout << "Linked List :" << "\n";
trav = head;
while(trav != NULL){
cout << (trav->data) << '\n';
trav = trav->next;
}
return 0;
}