Question

Given two sorted lists, L1 and L2, write a C++ function to compute L1 ∪ L2 using only the basic list operations.

Answer 1

#include <bits/stdc++.h>
using namespace std;

struct LLNode{
   int data;
   LLNode *next;  
};
void insertAtBeginning(LLNode**head,int dataToBeInserted);
//search function, says whether the element is present in that list or not
int search(LLNode *head, int data)
{
LLNode* temp = head;
while (temp != NULL) {
if (temp->data == data){
return 1;
}
temp = temp->next;
}
return 0;
}
//Finding the union of elements in two linked lists
//By checking whether the element in list2 is present in list1 or not
LLNode* findUnion(LLNode* list1, LLNode* list2)
{
LLNode* unionLL = NULL;
LLNode* temp1 = list1;
LLNode* temp2 = list2;
//Inserting all the elements in list1 to unionLL list
while(temp1 != NULL) {
insertAtBeginning(&unionLL, temp1->data);
temp1 = temp1->next;
}
//If element in list2 is not present in list1
//then inserting the element to unionLL list
while(temp2 != NULL) {
if (!search(list1, temp2->data))
{
insertAtBeginning(&unionLL, temp2->data);
}
temp2 = temp2->next;
}
return unionLL;
}