# Answer to Question #27337 in C++ for shahzad

Question #27337
Data Structures and Algorithm

Implement linkedlist for integers; following methods should be implemented.
void insertAtPosition(int x,int pos); //insert value x at given position
void insertAtEnd(int x); //insert value at the end of the list
void insertAtFront(int x); //insert value at the first position of the list
void removeFromFront(); //remove element from first position
void removeFromEnd(); //remove element from the end of the list
void removeFromPosition(int pos); //remove element from the position given by user. After the //operation there should be no gap in the elements of list
node* find(int x) const; //return the address
int findPosition(int pos) const; //find at given position and return the value
bool IsEmpty() const; //return true if list is empty
void print() const; //print the whole list
Note: Implement the main() to show that all above given methods are working properly
1
Expert's answer
2013-03-29T07:01:19-0400

/*
***********************
& The methods of the list
& is defined in the file
***********************
*/
#include "List.h" &
#include <iostream>
using namespace std;

Node::Node(int value){

m_value = value; &
next = NULL;
prev = NULL;
}

Node::~Node(){

}
int Node::GetValue(){
return m_value;
}

List::List(){

head = NULL;
tail = NULL;
count = 0;
}

List::~List(){
RemoveAll();
}

void List::InsertAtEnd(int x){

//create an instance of Node class
Node* node = new Node(x);

if(IsEmpty()) //if the list is empty
{
tail = node;
head = tail;
}
else //if the list is not empty
{
tail->next = node;
node->prev = tail;
tail = node;
}
count++; //increase size of the list
}
void List::InsertAtFront(int x){

//create an instance of Node class
Node* node = new Node(x);

if(IsEmpty()) & //if the list is empty
{
head = node;
tail = head;
}
else //if the list is not empty
{
head->prev = node;
node->next = head;
head = node;
}

count++;
}

void List::InsertAtPosition(int x, int pos){
&
& if(pos >= 0 && pos <= count - 1) //if pos is not less 0 and not more size of the list
& {
if(IsEmpty()|| pos == 0) //if list is empty or pos is 0 to insert x at the front of the list
InsertAtFront(x);
else
{
if(pos == count - 1) //if pos is count - 1 to insert x at the end of the list
InsertAtEnd(x);
else
{
Node* node = new Node(x);
Node* temp = head;
int i = 0;
while(i != pos){ //finding an element of the list
temp = temp->next;
i++;
}

& temp->prev->next = node; &
& node->prev = temp->prev;
& node->next = temp;
& temp->prev = node;
&
& count++;

}
}

& }
& else{
cout << endl << "Incorrect value of the position";
& }
}

void List::RemoveFromEnd(){

if(!IsEmpty()){
& //if the list is not empty
if(count > 1 && tail != NULL){ & //if the list has got more than one element
Node* temp = tail;

temp->prev->next = NULL;
tail = temp->prev;
delete temp;
count--;
& }
else if(count == 1 && tail != NULL) & //if the list has got one element
{
head = tail = NULL;
count--;
}
}
}

void List::RemoveFromFront(){

if(!IsEmpty()){ & //if the list is not empty

if(count > 1 && head != NULL){ //if the list has got more than one element
Node* temp = head;

head->next->prev = NULL;
head = temp->next;
delete temp;
count--;
& }
else if(count == 1 && head != NULL) & //if the list has got only one element
{
head = tail = NULL;
count--;
}
}
}

void List::RemoveFromPosition(int pos){

if(!IsEmpty()){ & //if the list is not empty

if(pos >=0 && pos <= count - 1){ & //if pos is not less 0 and pos is not more size of the list

if(pos == 0){ & //if the first element needs removing
RemoveFromFront();
}
else if(pos == count - 1) & //if the last element needs removing
{
RemoveFromEnd();
}
else & //if pos is not the first or the last element
{
Node* temp = head;
int i = 0;
while(i != pos)
{
temp = temp->next;
i++;
}
temp->next->prev = temp->prev;
temp->prev->next = temp->next;
delete temp;
count--;
}
}
else
cout << endl << "Incorrect position!";
}
}

void List::RemoveAll(){
& while(count != 0) &
& RemoveFromPosition();
}

bool List::IsEmpty() const
{ &
if(count == 0) //if size of the list is 0 to return true
return true;
else
return false; //if size of the list is not 0 to return false
}

int List::FindPosition(int x) const
{ &
if(!IsEmpty()){ //if the list is not empty

int i = 0;
Node* temp = head;
while(temp->next != NULL){ //finding an element to return it
if(temp->GetValue() == x) return i;
temp = temp ->next;
i++;
}
if(temp->GetValue() == x) return count - 1; & //if the element is the last element of the list
else
& return -1; //if such element do not exist
}
}

Node* List::Find(int x) const{

if(!IsEmpty()) & //if the list is not empty
{
Node* temp = head;
while(temp->next != NULL){
if(temp->GetValue() == x) return temp; &
temp = temp ->next;
}
if(temp->GetValue() == x) return temp;
else
& return NULL;
}
}

void List::Print() const{

if(!IsEmpty()){ //if the list is not empty
& &
Node* temp = head;
while(temp ->next != NULL){
cout << temp->GetValue() << ",";
temp = temp ->next;
}
cout << temp ->GetValue();
}
}

#include <iostream>
#include "List.h"
using namespace std;

int main(){
List* list = new List();

list->InsertAtEnd(4);
list->InsertAtFront(10);
list->InsertAtFront(3);
list->InsertAtPosition(5, 1);
list->InsertAtPosition(14, 2);
list->InsertAtPosition(13, 1);
list->Print();

list->RemoveFromEnd();
cout <<endl;
list->Print();
list->RemoveFromPosition(3);
list->RemoveFromPosition(4);
cout << endl;
list->Print();
list->RemoveFromFront();
cout << endl;
list->Print();
cout << endl;
cout << list->Find(10);
cout << endl;
cout << list->FindPosition(10);

list->RemoveFromEnd();
list->RemoveFromEnd();
list->RemoveFromEnd();
list->RemoveFromFront();
list->RemoveFromFront();
list->FindPosition(10);
list->Find(10);
delete list;
return 0;
}

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