I have the following code of LinkList and want to add the following two functions, please help me.

**removeTwoByTwoegg // Remove two head and two tails nodes**

duplicateEachNode // This is make A->B->C to A->A->B->B->C->C

```
#include <iostream>
using namespace std;
struct nodeType
{
int info;
nodeType *next;
};
class linkedListType
{
public:
linkedListType();
int listSize();
bool isEmpty();
int seqSearch(int);
void remove(int);
void insertFirst(int);
void insertEnd(int);
void insertAt(int, int);
void removeAt(int);
void print();
void clearList();
void insertOrdered(int);
void removeFirst();
void removeLast();
void removeLast2();
int removeOddSumEven();
~linkedListType();
private:
nodeType *first, *last;
int length;
};
// This function assumes that the list is NOT empty and first and last elements are NOT odd
int linkedListType::removeOddSumEven()
{
int sum = first->info;
nodeType *current = first->next;
nodeType *trailCurrent = first;
while(current != NULL)
{
if(current->info % 2 == 0)
{
sum += current->info;
trailCurrent = current;
current = current->next;
}
else
{
trailCurrent->next = current->next;
delete current;
length--;
current = trailCurrent->next;
}
}
return sum;
}
void linkedListType::removeLast()
{
if(length == 0)
cout<<"ERROR: EMPTY LIST" << endl;
else if(length == 1)
{
delete first;
last = first = NULL;
length--;
}
else
{
nodeType *current = first->next;
nodeType *trailCurrent = first;
while(current != last)
{
trailCurrent = current;
current = current->next;
}
delete current;
trailCurrent->next = NULL;
last = trailCurrent;
length--;
}
}
void linkedListType::removeLast2()
{
if(length == 0)
cout<<"ERROR: EMPTY LIST" << endl;
else if(length == 1)
{
delete first;
last = first = NULL;
length--;
}
else
{
nodeType *current = first;
while(current->next != last)
current = current->next;
delete last;
current->next = NULL;
last = current;
length--;
}
}
void linkedListType::removeFirst()
{
if(length == 0)
cout<<"ERROR: EMPTY LIST" << endl;
else if(length == 1)
{
delete first;
last = first = NULL;
length--;
}
else
{
nodeType *current = first;
first = first->next;
delete current;
length--;
}
}
linkedListType::linkedListType()
{
first = last = NULL;
length = 0;
}
int linkedListType::listSize()
{
return length;
}
bool linkedListType::isEmpty()
{
return (length == 0);
}
int linkedListType::seqSearch(int item)
{
nodeType *current = first;
int loc = 0;
while(current != NULL)
{
if(current->info == item)
return loc;
current = current->next;
loc++;
}
return -1;
}
void linkedListType::remove(int item)
{
if(isEmpty())
{
cout<<"Can not remove from empty list\n";
return;
}
nodeType *current, *trailCurrent;
if(first->info == item)//delete the first element, special case
{
current = first;
first = first->next;
delete current;
length--;
if(length == 0)
last = NULL;
}
else
{
current = first->next;
trailCurrent = first;
while(current != NULL)
{
if(current->info == item)
break;
trailCurrent = current;
current = current->next;
}
if(current == NULL)
cout<<"The item is not there\n";
else
{
trailCurrent->next = current->next;
if(last == current) //delete the last item
last = trailCurrent;
delete current;
length--;
}
}
}
void linkedListType::insertFirst(int item)
{
nodeType *newNode = new nodeType;
newNode->info = item;
if(length == 0){
first = last = newNode;
newNode->next = NULL;
}
else{
newNode->next = first;
first = newNode;
}
length++;
}
void linkedListType::insertEnd(int item)
{
nodeType *newNode = new nodeType;
newNode->info = item;
if(length == 0){
first = last = newNode;
newNode->next = NULL;
}
else{
last->next = newNode;
newNode->next = NULL;
last = newNode;
}
length++;
}
void linkedListType::insertAt(int loc, int item)
{
if(loc < 0 || loc > length)
cout<< "ERROR: Out of range" << endl;
else
{
nodeType *newNode = new nodeType;
newNode->info = item;
if (loc == 0) //insert at the begining
insertFirst(item);
else if (loc == length) //insert at the end;
insertEnd(item);
else
{
nodeType *current = first;
for(int i = 1; i < loc; i++)
current = current->next;
newNode->next = current->next;
current->next = newNode;
length++;
}
}
}
void linkedListType::removeAt(int loc)
{
if(loc < 0 || loc >= length)
cout<< "ERROR: Out of range" << endl;
else
{
nodeType *current, *trailCurrent;
if(loc == 0) //remove the first item
{
current = first;
first = first->next;
delete current;
length--;
if(length == 0)
last = NULL;
}
else
{
current = first->next;
trailCurrent = first;
for(int i = 1; i < loc; i++)
{
trailCurrent = current;
current = current->next;
}
trailCurrent->next = current->next;
if(last == current) //delete the last item
last = trailCurrent;
delete current;
length--;
}
}
}
void linkedListType::print()
{
nodeType *current = first;
while(current != NULL)
{
cout<<current->info <<endl;
current= current->next;
}
}
void linkedListType::clearList()
{
nodeType *current;
while(first != NULL)
{
current = first;
first = first->next;
delete current;
}
last = NULL;
length = 0;
}
void linkedListType::insertOrdered(int item)
{
nodeType *newNode = new nodeType;
newNode->info = item;
if(first == NULL)
{
first = last = newNode;
newNode->next = NULL;
length++;
}
else if(first->info >= item)
{
newNode->next = first;
first = newNode;
length++;
}
else
{
nodeType *current = first->next;
nodeType *trailCurrent = first;
while(current != NULL)
{
if(current->info >= item)
break;
current = current->next;
trailCurrent = trailCurrent->next;
}
if(current == NULL) //insert at the end
{
last->next = newNode;
newNode->next = NULL;
last = newNode;
length++;
}
else
{
trailCurrent->next = newNode;
newNode->next = current;
length++;
}
}
}
linkedListType::~linkedListType()
{
clearList();
}
int main()
{
linkedListType l1;
l1.insertAt(0, 10);
l1.insertAt(1, 1);
l1.insertAt(2, 3);
l1.insertAt(3, 40);
l1.print();
return 0;
}
```