I am writing a function to delete a give number from a linked list in codefights. I am passing 6 out of 7 test cases, however, the 7th is hidden so I am not able to see what it is I am doing wrong. Can anyone see what test case I am missing with this function?
// Definition for singly-linked list:
// template<typename T>
// struct ListNode {
// ListNode(const T &v) : value(v), next(nullptr) {}
// T value;
// ListNode *next;
// };
#include <stdio.h>
ListNode<int> * removeKFromList(ListNode<int> * l, int k) {
ListNode<int> *cur = l;
ListNode<int> *temp = l;
while (cur != NULL) {
if (cur->value == k) {
if (cur == l) {
ListNode<int> *del;
del = cur;
cur = cur->next;
l = l->next;
temp = temp->next;
delete del;
} else {
ListNode<int> *del = cur;
cur = cur->next;
temp->next = cur;
delete del;
}
} else {
temp = cur;
cur = cur->next;
}
}
return l;
}
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I am trying to make a quicksort algorithm for singly-linked lists. I, however, must be somehow creating a cyclical list in the process. In the concatenate function, the while loop gets stuck printing out 2 and 22 continuously. So, I assume that I must somehow be creating a list where Node 2 points to Node 22 and vice versa. Unfortunately, I have no idea how, since I feel like I have added nullptr to the end of every list where it would matter. I have reviewed my partition function so many times I add more bugs than I fix. Is there something I am missing with how linked lists work?
I have been stuck on this for a while so any help would be greatly appreciated.
Here is my quicksort code.
// quick.cpp
#include "volsort.h"
#include <iostream>
#include <string>
using namespace std;
// Prototypes
Node *qsort(Node *head, bool numeric);
void partition(Node *head, Node *pivot, Node *&left, Node *&right, bool numeric);
Node *concatenate(Node *left, Node *right);
// Implementations
void quick_sort(List &l, bool numeric) {
l.head = qsort(l.head, numeric);
}
Node *qsort(Node *head, bool numeric) {
if (head == nullptr || head->next == nullptr) {
return head;
}
Node *l = nullptr;
Node *r = nullptr;
partition(head, head, l, r, numeric);
l = qsort(l, numeric);
r = qsort(r, numeric);
head = concatenate(l, head);
head = concatenate(head, r);
return head;
}
void partition(Node *head, Node *pivot, Node *&left, Node *&right, bool numeric) {
Node *cur = pivot->next;
bool c;
Node *tl=nullptr, *tr=nullptr;
while (cur != pivot && cur != nullptr) {
if (numeric) {
c = node_number_compare(cur, pivot);//compare numeric elements of the Nodes
}
else {
c = node_string_compare(cur, pivot);//compare string elements of the code
}
if (c) {
if (left == nullptr) {
left = cur;
cur = cur->next;
tl = left;
}
else {
tl->next = cur;
cur = cur->next;
tl = tl->next;
tl->next = nullptr;
}
}
else {
if (right == nullptr) {
right = cur;
cur = cur->next;
tr = right;
}
else {
tr->next = cur;
cur = cur->next;
tr = tr->next;
tr->next = nullptr;
}
}
}
}
Node *concatenate(Node *left, Node *right) {
if (right == nullptr && left == nullptr) {
return nullptr;
}
else if (left == nullptr) {
right->next = nullptr;
return right;
}
else if (right == nullptr) {
left->next = nullptr;
return left;
}
Node *t = left;
while (t->next != nullptr) {
cout << t->number << endl;
t = t->next;
}
t->next = right;
while (t->next != nullptr) {
cout << t->number << endl;
t = t->next;
}
t->next = nullptr;
return left;
}
Input:
45
4
9
22
2
Here's the list class functions if it helps.
#include "volsort.h"
#include <string>
#include <iostream>
List::List() {
head = NULL;
size = 0;
}
List::~List() {
if (head != NULL) { // follow the links, destroying as we go
Node *p = head;
while (p != NULL) {
Node *next = p->next; // retrieve this node's "next" before destroy it
delete p;
p = next;
}
}
}
bool node_number_compare(const Node *a, const Node *b) {
if (a->number <= b-> number) {
return true;
}
else {
return false;
}
}
bool node_string_compare(const Node *a, const Node *b) {
return a->string <= b->string;
}
void List::push_front(const std::string &s) {
Node *node = new Node();
node->next = NULL;
node->string = s;
node->number = std::stoi(s);
if (head == NULL) {
head = node;
size = 1;
}
else {
Node *p = head;
while (p->next != NULL) {p = p->next;} // go to end of list
p->next = node;
size++;
}
}
void List::dump_node(Node *n) {
while (n->next != NULL) {
std::cout << n->number << " " << n->string << std::endl;
}
}
I want to use subscript operator overloading in linklist but everytime it give me Segmentation fault (core dumped) ERROR! MY TASK IS : (Overload [] operator. Use for loop in main to display it.) I ALSO PROVIDING THE TASK LINK BELOW
//task link
[LINK OF TASK] https://anonymfile.com/r1XKK/dsa-a3.pdf
//MY CODE IS :
#include <iostream>
using namespace std;
class LinkedList
{
private:
class Node
{
public:
int data;
Node * next;
Node(int data)
{
this->data = data;
this->next = NULL;
}
};
public:
Node *head;
LinkedList(){
head = NULL;
}
//Write a copy constructor. Also copy must be deep.
LinkedList(LinkedList& S)
{
head = S.head;
}
//Overload [] operator. Use for loop in main to display it.
void operator[](int i) {
head->data = i;
}
void InsertAtEnd(int data){
if (head == NULL)
{
head = new Node(data);
return;
}
Node * temp = head;
while (temp->next != NULL)
{
temp = temp->next;
}
temp->next = new Node(data);
}
void Insert(int d1, int d2)//Add the node of data d2 after the node with data d1. If d2 is not available add it to the end.
{
if (head == NULL)
{
Node * n = new Node(d2);
n->next = head;
head = n;
return;
}
Node * temp = head;
while (temp != NULL)
{
if (temp->data == d1)
{
Node * temp1 = temp->next;
temp->next = new Node(d2);
temp->next->next = temp1;
}
temp = temp->next;
}
}
void Delete(int data){
Node * todelete;
if(head->data == data){
todelete = head;
head = head->next;
free(todelete);
return;
}
Node *temp = head;
while(temp->next != NULL){
if(temp->next->data == data){
todelete = temp->next;
temp->next = temp->next->next;
free(todelete);
break;
}
temp = temp->next;
}
} // Deletes a node with data.
int getSize(){
Node * temp = head;
int size = 0;
while(temp != NULL){
temp = temp->next;
size++;
}
return size;
} //returns the count of elements in the list
bool IsEmpty(){
if(head == NULL){
return true;
}
else{
return false;
}
} //Returns true if empty.
void Merge(Node * list){
//merge
Node * temp = head;
while(temp != NULL){
if(temp->next == NULL and list != NULL){
temp->next = list;
break;
}
temp = temp->next;
}
//DISPLAY
while(head!=NULL){
cout<<head->data<<"->";
head=head->next;
}
cout<<"NULL"<<endl;
} //Merges the to the calling class.
void Erase(){
Node * erase;
while(head!= NULL){
erase = head;
head = head->next;
head = NULL;
}
free(erase);
} //Deletes every node in an array.
void SelectiveErase(int num) //Find num and delete everything after num.
{
Node * temp = head;
Node * todelete;
while(temp != NULL){
if(temp->data == num){
Node * erase = temp->next;
while(temp->next != NULL){
erase = temp->next;
temp->next = temp->next->next;
temp->next = NULL;
}
free(erase);
break;
}
temp = temp->next;
}
}
int FindNCount(int find)//Find and return count of all occurrence.
{
int counter = 0;
bool flag = false;
Node * temp = head;
while(temp->data!= find){
temp = temp->next;
counter++;
}
return counter;
}
int RemoveDuplicate(int find)//Find and remove every duplicate element in the list. Make //elements unique.
{
Node * temp = head;
Node *temp1;
while(temp != NULL){
temp1 = temp;
while(temp1->next != NULL){
if(temp->data == temp1->next->data and temp->data == find and temp1->next->data == find){
Node *todelete = temp1->next;
temp1->next = temp1->next->next;
free(todelete);
}
else{
temp1 = temp1->next;
}
}
temp = temp->next;
}
return find;
}
void FindNReplace(int find, int data)//Find and replace all occurrence recursively.
{
Node * temp = head;
while(temp != NULL){
if(temp->data == find){
temp->data = data;
break;
}
temp = temp->next;
}
}
void Display(){
static Node * temp= head;
if(temp == NULL){ cout << "NULL" << endl; return;}
cout << temp->data<<"->";
temp = temp->next;
Display();
}
};
void Swap() // swap the contents of one list with another list of same type and size. Also write parameter
{
LinkedList L,L1;
cout<<"AFTER SWAPING THE VALUE OF FIRST LIST \n";
while(L.head != NULL && L1.head != NULL){
int temp = L.head->data;
L.head->data = L1.head->data;
L1.head->data = temp;
cout<<L.head->data<<"\n";
L.head = L.head->next;
L1.head = L1.head->next;
}
cout<<endl;
}
int main()
{
// You must call Display function after every function.
LinkedList L{};
L[23];
// LinkedList L1;
// L1.InsertAtEnd(5);
// L1.InsertAtEnd(6);
//L.Erase();
// cout<<L.FindNCount(1)<<endl;
//L.SelectiveErase(2);
//L.Display();
//L.Merge(L1.head);
//L.RemoveDuplicate(2);
//L.Display();
//Swap();
return 0;
}
Overloading the subscript operator should return something. The assignment looks a bit vague, but I hope this will fix it:
//Overload [] operator. Use for loop in main to display it.
Node* operator[](int i) {
Node* nodePtr = head;
int counter = 0;
while (nodePtr != NULL && counter != i) {
nodePtr = nodePtr->next;
counter++;
}
return nodePtr;
}
I have previously posted some part of this task here.
I am now implementing a method that removes an element at a given index. My code is
void remove(int index)
{
if (head != NULL)
{
Node *current = get_node(index);
Node *prev = get_node(index - 1);
Node *next = get_node(index + 1);
prev->next = current->next;
delete current;
}
}
however, I am facing this error message
libc++abi.dylib: terminating with uncaught exception of type
std::range_error: IndexError: Index out of range
Abort trap: 6
I am guessing the problem is the pointers, but I am not sure why this is not working. Anyone who can help?
I think you can handle corner cases like this:
#include <iostream>
using namespace std;
struct Node {
Node(int val) {
this->val = val;
}
struct Node * next;
int val;
};
class LinkedList {
public:
Node* head;
LinkedList() {
head = new Node(1);
Node * n1 = new Node(2);
head->next = n1;
Node * n2 = new Node(3);
n1->next = n2;
}
void remove(int index) {
if (head == NULL) {
return;
}
int pos = 0;
Node * cur = head;
Node *prev = NULL;
while (cur != NULL) {
if (pos == index) {
break;
}
pos++;
prev = cur;
cur = cur->next;
}
if (prev == NULL) {
head = head->next;
}
else {
prev->next = cur->next;
}
delete cur;
}
};
void print(Node * head){
cout << "Current linked list:\n";
while(head != NULL) {
cout << head->val << endl;
head = head->next;
}
cout << endl;
}
int main() {
LinkedList * list = new LinkedList();
print(list->head);
list->remove(0);
print(list->head);
list->remove(1);
print(list->head);
list->remove(0);
print(list->head);
}
I am working in c++. I'm attempting to make my own iterator for a templated linked list class (without using the STL), but I seem to have trouble using "friends." I want to OListIterator to have access to the "Node" struct within the list class. If anyone could help it would be greatly appreciated!
OListIterator:
#ifndef pg6ec_OListIterator_h
#define pg6ec_OListIterator_h
#include "OList.h"
template <typename T>
class OListIterator
{
private:
T * value;
T * next;
public:
OListIterator()
{}
void setValue(T & val, T & n)
{
value = &val;
next = &n;
}
int operator*()
{
return *value;
}
bool operator==(OListIterator<T> other)
{
return value == other.value && next == other.next;
}
bool operator!=(OListIterator<T> other)
{
return value != other.value && next != other.next;
}
void operator+=(int x)
{
}
};
#endif
List:
#ifndef pg6OList_OListBlah_h
#define pg6OList_OListBlah_h
#include <stdio.h>
#include <stdlib.h>
#include "OListIterator.h"
template <typename T>
class list
{
private:
typedef struct node
{
T value;
struct node * next;
}Node;
Node * root;
public:
list()
{
root = NULL;
}
list(const list & other)
{
Node * temp = other.returnRoot();
Node * currSpot = NULL;
root = new Node;
root->value = temp->value;
currSpot = root;
temp = temp->next;
while (temp)
{
currSpot->next = new Node;
currSpot = currSpot->next;
currSpot->value = temp->value;
temp = temp->next;
}
}
~list()
{
clear();
};
void clear()
{
Node * delNode = root;
while (delNode)
{
root = root->next;
delete delNode;
delNode = root;
}
delete root;
};
Node * returnRoot() const
{
return this->root;
}
int size()
{
int ans = 0;
if (root == NULL)
{
return ans;
}
Node * top = root;
while (top)
{
ans++;
top = top->next;
}
return ans;
}
bool insert(T & item)
{
if (root == NULL)
{
root = new Node;
root->value = item;
return true;
}
else
{
Node * curr = root;
Node * prev = NULL;
while (curr)
{
if ( curr->value > item )
{
Node * insertion = new Node;
insertion->value = item;
if (prev)
{
insertion->next = curr;
prev->next = insertion;
}
else
{
root = insertion;
root->next = curr;
}
return true;
}
else if ( curr->value == item )
{
Node * insertion = new Node;
insertion->value = item;
insertion->next = curr->next;
curr->next = insertion;
return true;
}
prev = curr;
if (curr->next)
{
curr = curr->next;
}
else if ( curr->next == NULL )
{
curr->next = new Node;
curr->next->next = NULL;
curr->next->value = item;
return true;
}
}
}
return false;
}
T get(int x)
{
T ans = root->value;
if (x > size() || x < 0)
{
return ans;
}
Node * curr = root;
for (int i = 0; i < size(); i++)
{
if (i == x)
{
ans = curr->value;
break;
}
curr = curr->next;
}
return ans;
}
int count(T base)
{
int num = 0;
Node * curr = root;
while (curr)
{
if (curr->value == base)
{
num++;
}
curr = curr->next;
}
return num;
}
bool remove(T base)
{
Node * curr = root;
Node * prev = NULL;
if (root->value == base)
{
delete this->root;
root = root->next;
return true;
}
while (curr)
{
if (curr->value == base)
{
Node * temp = new Node;
if (curr->next)
{
T val = curr->next->value;
temp->value = val;
temp->next = curr->next->next;
}
delete curr;
delete curr->next;
prev->next = temp;
return true;
}
prev = curr;
curr = curr->next;
}
return false;
}
void uniquify()
{
Node * curr = root;
Node * next = root->next;
while (curr)
{
while (next && curr->value == next->value)
{
Node * temp = new Node;
if (next->next)
{
T val = next->next->value;
temp->value = val;
temp->next = next->next->next;
delete next;
delete next->next;
curr->next = temp;
next = curr->next;
}
else
{
delete temp;
delete temp->next;
curr->next = NULL;
delete next;
delete next->next;
break;
}
}
curr = curr->next;
if (curr)
next = curr->next;
}
}
OListIterator<T> begin()
{
OListIterator<T> it;
it.setValue(root->value, root->next->value);
return it;
}
OListIterator<T> end()
{
Node * curr = root;
for (int i = 0; i < size(); i++)
{
curr = curr->next;
}
OListIterator<T> it;
it.setValue(curr->value);
return it;
}
};
#endif
I want to OListIterator to have access to the "Node" struct within the list class.
For this, you need to forward-declare the iterator class:
template<typename T> OListIterator;
template <typename T>
class list
{
friend class OListIterator<T>;
//... the rest
}
Alternatively, you can use a template friend declaration, but then any OListIterator type has access to any list type:
template <typename T>
class list
{
template<typename U> friend class OListIterator;
//... the rest
}
Here is a more verbose but unrelated-to-your-code example:
template<typename T> struct Iterator;
template<typename T>
struct List
{
friend struct Iterator<T>;
List(T i) : somePrivateMember(i) {}
private:
T somePrivateMember;
};
template<typename T>
struct Iterator
{
Iterator(List<T> const& list) {std::cout<<list.somePrivateMember<<std::endl;}
};
int main()
{
List<int> list(1);
Iterator<int> iterator(list);
}
The constructor of the Iterator class prints the private member somePrivateMember, whose value is 1.
I wrote this LinkedList template class, which isn't finished yet- I have yet to add safety features and more methods. As of now it does what I need it to. But it fails in a certain situation and I don't know why.
template<class data_type> class LinkedList {
private:
struct Node {
data_type data;
Node* prev;
Node* next;
Node() : prev(NULL), next(NULL) {}
};
Node* head;
Node* GetLastNode() {
Node* cur = head;
while (cur->next != NULL)
cur = cur->next;
return cur;
}
public:
LinkedList() {
head = new Node;
head->prev = head;
head->next = NULL;
}
LinkedList(LinkedList<data_type> &to_copy) {
head = new Node;
head->prev = head;
head->next = NULL;
for (int i = 1; i <= to_copy.NumberOfItems(); i++) {
this->AddToList(to_copy.GetItem(i));
}
}
~LinkedList() {
DeleteAll();
delete head;
head = NULL;
}
void AddToList(const data_type data) {
Node* last = GetLastNode();
Node* newnode = last->next = new Node;
newnode->prev = last;
newnode->data = data;
}
void Delete(const unsigned int position) {
int currentnumberofitems = NumberOfItems();
Node* cur = head->next;
int pos = 1;
while (pos < position) {
cur = cur->next;
pos++;
}
cur->prev->next = cur->next;
if (position != currentnumberofitems)
cur->next->prev = cur->prev;
delete cur;
}
void DeleteAll() {
Node* last = GetLastNode();
Node* prev = last->prev;
while (prev != head) {
delete last;
last = prev;
prev = last->prev;
}
head->next = NULL;
}
data_type GetItem(unsigned int item_number) {
Node* cur = head->next;
for (int i = 1; i < item_number; i++) {
cur = cur->next;
}
return cur->data;
}
data_type* GetItemRef(unsigned int item_number) {
Node* cur = head->next;
for (int i = 1; i < item_number; i++) {
cur = cur->next;
}
return &(cur->data);
}
int NumberOfItems() {
int count(0);
Node* cur = head;
while (cur->next != NULL) {
cur = cur->next;
count++;
}
return count;
}
};
I stated my problem in the question and here is an example:
class theclass {
public:
LinkedList<int> listinclass;
};
void main() {
LinkedList<theclass> listoftheclass;
theclass oneclass;
oneclass.listinclass.AddToList(5);
listoftheclass.AddToList(oneclass);
cout << listoftheclass.GetItem(1).listinclass.GetItem(1);
}
I can't figure out why it doesn't run right.
You need to implement an assignment operator. The problem starts in this function here:
void AddToList(const data_type data) {
Node* last = GetLastNode();
Node* newnode = last->next = new Node;
newnode->prev = last;
newnode->data = data; <---------------------------- Right there
}
Since data_type is your class, and you don't have an appropriate assignment operator, you are just getting a member by member(shallow) copy there.
See The Rule of Three
You should also probably implement a swap function, and have your assignment operator use that.
See Copy and Swap Idiom
In C++03, local classes can't be template arguments. Move theclass outside of main, and it will work.
In C++0x this limitation is removed.