Linked List

• Remove Duplicate Elements ```c++ //https://www.geeksforgeeks.org/remove-duplicates-from-an-unsorted-linked-list/ /* C++ Program to remove duplicates in an unsorted linked list */ #include <bits/stdc++.h> using namespace std;

struct Node { int data; struct Node *next; };

struct Node *newNode(int data) { Node *temp = new Node; temp->data = data; temp->next = NULL; return temp; }

void removeDuplicatesNoSpace(struct Node *head) { struct Node *ptr1, *ptr2, *temp; ptr1 = head;

while (ptr1 != NULL && ptr1->next != NULL)
{
    ptr2 = ptr1;

    while (ptr2->next != NULL)
    {
        if (ptr1->data == ptr2->next->data)
        {
            temp = ptr2->next;
            ptr2->next = ptr2->next->next;
            delete temp;
        }
        else
        {
            ptr2 = ptr2->next;
        }
    }

    ptr1 = ptr1->next;  
} }

void removeDuplicates(struct Node *start) { std::unordered_map<int, bool> m; struct Node *ptr = NULL;

while (start != NULL)
{
    if (m.find(start->data) != m.end())
    {
        ptr->next = start->next;
    }
    else
    {
        m.insert({start->data, true});
        ptr = start;
    }
    start = start->next;
} }

/* Function to print nodes in a given linked list */ void printList(struct Node *node) { while (node != NULL) { printf(“%d “, node->data); node = node->next; } }

/* Driver program to test above function / int main() { / The constructed linked list is: 10->12->11->11->12->11->10*/ struct Node *start = newNode(10); start->next = newNode(12); start->next->next = newNode(11); start->next->next->next = newNode(11); start->next->next->next->next = newNode(12); start->next->next->next->next->next = newNode(11); start->next->next->next->next->next->next = newNode(10); start->next->next->next->next->next->next->next = newNode(15); start->next->next->next->next->next->next->next->next = newNode(15);

printf("Linked list before removing duplicates ");
printList(start);

removeDuplicatesNoSpace(start);

printf("\nLinked list after removing duplicates ");
printList(start);

return 0; }

```