C++ Program For Removing All Occurrences Of Duplicates From A Sorted Linked List

// C++ program to remove all occurrences 
// of duplicates from a sorted linked list.
#include <bits/stdc++.h>
using namespace std;

// A linked list node
struct Node
{
    int data;
    struct Node *next;
};

// Utility function 
// to create a new Node
struct Node *newNode(int data)
{
    Node *temp = new Node;
    temp -> data = data;
    temp -> next = NULL;
    return temp;
}

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

// Function to remove all occurrences
// of duplicate elements
void removeAllDuplicates(struct Node* &start)
{
    // Create a dummy node that acts like 
    // a fake head of list pointing to the 
    // original head
    Node* dummy = new Node;

    // Dummy node points to the original head
    dummy -> next = start;
    
    // Node pointing to last node which has 
    // no duplicate.
    Node* prev = dummy;
    
    // Node used to traverse the linked list.
    Node* current = start;

    while(current != NULL)
    {
        // Until the current and previous 
        // values are same, keep updating current
        while(current -> next != NULL &&
              prev -> next -> data == current -> next -> data)
            current = current -> next;

        // if current has unique value 
        // i.e current is not updated, 
        // Move the prev pointer to 
        // next node
        if (prev -> next == current)
            prev = prev -> next;

        // When current is updated to the 
        // last duplicate value of that segment, 
        // make prev the next of current
        else
            prev -> next = current -> next;

        current = current -> next;
    }

    // Update original head to the next 
    // of dummy node 
    start = dummy -> next;
}

// Driver Code
int main() 
{
    // 23->28->28->35->49->49->53->53
    struct Node* start = newNode(23);
    start -> next = newNode(28);
    start -> next -> next = newNode(28);
    start -> next -> 
             next -> next = newNode(35);
    start -> next -> 
    next -> next -> next = newNode(49);
    start -> next -> 
    next -> next -> 
    next -> next = newNode(49);
    start -> next -> 
    next -> next -> 
    next -> next -> next = newNode(53);
    start -> next -> 
    next -> next -> 
    next -> next -> 
    next -> next = newNode(53);
    cout << "List before removal " <<
            "of duplicates";
    printList(start);
    
    removeAllDuplicates(start);
    
    cout << "List after removal " << 
            "of duplicates";
    printList(start);
    return 0;
}
// This code is contributed by NIKHIL JINDAL