Question

I have a problem with merging the two linked lists together. In the function AscendMerge, I am trying to compare the values of each node in the two lists and output them into one list in ascended order. Everything works except for the one function. Can someone tell me what im doing wrong, when I run it it skips over values.

#include <iostream>
#include <cassert>
using namespace std;
struct nodeType
{
   int info;
   nodeType *link;
   nodeType *current;
   nodeType *prev;
};

class linkedListType
{
public:

   nodeType *first;
   nodeType* head;
   nodeType * end;
   nodeType *last;
   int count;
   void print() const;
   void insertList1(const int newItem);
   void insertList2(const int newItem);
   void printList2()const;
   void AscendMerge();
   linkedListType();
};
linkedListType::linkedListType() //default constructor
{
   first = NULL;
   last = NULL;
   count = 0;
}

void linkedListType::print() const
{
   nodeType *current; //pointer to traverse the list

   current = first; //set current so that it points to
                       //the first node
   while (current != NULL) //while more data to print
   {
       cout << current->info << " ";
       current = current->link;
   }
}//end print

void linkedListType::AscendMerge()
{
   nodeType * c1;
   nodeType * c2;
   nodeType * p1;
   nodeType * p2;
   c1 = first;
   c2 = head;
   p1 = first;
   p2 = head;
   while (head->link&&first->link != NULL)
   {
       if (c2->info<c1->info)
       {
           c2->link = p1->link;
          
       }
       else
       {
           c1->link=p2->link;
       }
       p1 = p1->link;
       p2 = p2->link;
       c1 = c1->link;
       c2 = c2->link;

       cout << c2->info<< " ";
   }

}
void linkedListType::insertList1(const int newItem)
{
   int count = 0;
   if (first == NULL)
   {
       first = new nodeType;
       first->info = newItem;
       first->link = NULL;
       last = first;
       count++;
   }
   else {
       last->link = new nodeType;
       last->link->info = newItem;
       last->link->link = NULL;
       last = last->link;
       count++;
   }
}

void linkedListType::insertList2(const int newItem)
{
   int count = 0;
   if (head == NULL)
   {
       head = new nodeType;
       head->info = newItem;
       head->link = NULL;
       end = head;
       count++;
   }
   else {
       end->link = new nodeType;
       end->link->info = newItem;
       end->link->link = NULL;
       end = end->link;
       count++;
   }
}

void linkedListType::printList2()const
{
   nodeType *current; //pointer to traverse the list

   current = head; //set current so that it points to
                       //the first node
   while (current != NULL) //while more data to print
   {
       cout << current->info << " ";
       current = current->link;
   }
}

//Implementation//

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

int main()
{
   linkedListType list;
   int num;
   bool found = false;

   cout << "Enter numbers ending with -999" << endl;
   cin >> num;

   while (num != -999)
   {
       list.insertList1(num);
       cin >> num;
   }

   cout << endl;
   cout << "Enter numbers for second list ending with -999" << endl;
   cin >> num;
   while (num != -999)
   {
       list.insertList2(num);
       cin >>num;
   }
   cout << "List1: ";
   list.print();
   cout << endl;
   cout << "List2: ";
   list.printList2();
   cout << endl;
   list.AscendMerge();
  
   return 0;
}

Answer 1

when you initialized first and head to both c1 and p2, the values are same. This is because, we just initialized one variable first and head in the class and hence when to assign that head or first same value is copied in both. If you want to get two lists then you need to pass one list as argument and then append the values based on the condition. I wrote the new code. You can check this:

//Main.cpp

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

int main()
{
linkedListType list1,list2;
int num;
bool found = false;

cout << "Enter numbers ending with -999" << endl;
cin >> num;

while (num != -999)
{
list1.insertList(num);
cin >> num;
}

cout << endl;
cout << "Enter numbers for second list ending with -999" << endl;
cin >> num;
while (num != -999)
{
list2.insertList(num);
cin >>num;
}
cout << "List1: ";
list1.print();
cout << endl;
cout << "List2: ";
list2.print();
cout << endl;
list1.AscendMerge(list2);
return 0;
}

//Merge.h

#include <iostream>
using namespace std;
struct nodeType
{
int info;
nodeType *link;
nodeType *current;
nodeType *prev;
};

class linkedListType
{
public:

nodeType *first;
nodeType* head;
nodeType * end;
nodeType *last;
int count;
void print() const;
void insertList(const int newItem);
void AscendMerge(linkedListType l);

linkedListType();
};
linkedListType::linkedListType() //default constructor
{
first = NULL;
last = NULL;
count = 0;
}

void linkedListType::print() const
{
nodeType *current; //pointer to traverse the list

current = first; //set current so that it points to
//the first node
while (current != NULL) //while more data to print
{
cout << current->info << " ";
current = current->link;
}
}//end print

void linkedListType::AscendMerge(linkedListType l)

{
this->print();
l.print();
nodeType * c2;
nodeType * p2;
linkedListType newList;
c2 = this->first;
p2 = l.first;
while (c2!=NULL && p2!=NULL)
{
if (c2->info < p2->info)
{
newList.insertList(c2->info);
c2 = c2->link;
}
else if(c2->info > p2->info)
{
newList.insertList(c2->info);
p2 = p2->link;
}
else
{
newList.insertList(c2->info);
newList.insertList(p2->info);
c2 = c2->link;
p2 = p2->link;
}
}
while(c2!=NULL)
{
newList.insertList(c2->info);
c2 = c2->link;
}
while(p2!=NULL)
{
newList.insertList(c2->info);
p2 = p2->link;
}
newList.print();
}
void linkedListType::insertList(const int newItem)
{
int count = 0;
if (first == NULL)
{
first = new nodeType;
first->info = newItem;
first->link = NULL;
last = first;
count++;
}
else {
last->link = new nodeType;
last->link->info = newItem;
last->link->link = NULL;
last = last->link;
count++;
}
}