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merge2sortedLinkedLists.cpp
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merge2sortedLinkedLists.cpp
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#include <bits/stdc++.h>
using namespace std;
class node
{
public:
int data;
node *next;
node(int val)
{
data = val;
next = NULL;
}
};
void insertAtTail(node *&head, int val)
{
node *newNode = new node(val); // created a new node;
if (head == NULL)
{
head = newNode;
return;
// here you can simply call insertAtBeginning
}
node *temp = head;
while (temp->next != NULL)
{
temp = temp->next;
}
temp->next = newNode;
// as our new node already points to NULL in its next so we simply do nothing
}
node *mergeLL(node *&headLL1, node *&headLL2)
{
node *ptr1 = headLL1;
node *ptr2 = headLL2;
node *dummyNode = new node(-1);
node *ptr3 = dummyNode;
while (ptr1 != NULL && ptr2 != NULL)
{
if (ptr1->data <= ptr2->data)
{
ptr3->next = ptr1;
ptr1 = ptr1->next;
ptr3 = ptr3->next;
}
else
{
ptr3->next = ptr2;
ptr2 = ptr2->next;
ptr3 = ptr3->next;
}
}
while (ptr1 != NULL)
{
ptr3->next = ptr1;
ptr1 = ptr1->next;
ptr3 = ptr3->next;
}
while (ptr2 != NULL)
{
ptr3->next = ptr2;
ptr2 = ptr2->next;
ptr3 = ptr3->next;
}
return dummyNode->next;
}
node *mergeLLRecursive(node *&headLL1, node *&headLL2)
{
if (headLL1 == NULL)
{
return headLL2;
}
if (headLL2 == NULL)
{
return headLL1;
}
node *result;
if (headLL1->data <= headLL2->data)
{
result = headLL1;
result->next = mergeLLRecursive(headLL1->next, headLL2);
}
else
{
result = headLL2;
result->next = mergeLLRecursive(headLL1, headLL2->next);
}
return result;
}
void display(node *head)
{
if (head == NULL)
{
cout << "NULL" << endl;
return;
}
node *temp = head;
while (temp != NULL)
{
cout << temp->data << "->";
temp = temp->next;
}
cout << "NULL" << endl;
}
int main()
{
node *headLL1 = NULL;
node *headLL2 = NULL;
insertAtTail(headLL1, 1);
insertAtTail(headLL1, 4);
insertAtTail(headLL1, 5);
insertAtTail(headLL1, 7);
insertAtTail(headLL2, 2);
insertAtTail(headLL2, 3);
insertAtTail(headLL2, 6);
display(headLL1);
display(headLL2);
node *newHead = mergeLLRecursive(headLL1, headLL2);
display(newHead);
return 0;
}