Remove duplicates from an unsorted doubly linked list | C ++ implementation to remove duplicates from an unsorted doubly linked list ; a node of the doubly linked list ; Function to delete a node in a Doubly Linked List . head_ref -- > pointer to head node pointer . del -- > pointer to node to be deleted . ; base case ; If node to be deleted is head node ; Change next only if node to be deleted is NOT the last node ; Change prev only if node to be deleted is NOT the first node ; function to remove duplicates from an unsorted doubly linked list ; if doubly linked list is empty ; unordered_set ' us ' implemented as hash table ; traverse up to the end of the list ; if current data is seen before ; store pointer to the node next to ' current ' node ; delete the node pointed to by ' current ' ; update ' current ' ; insert the current data in ' us ' ; move to the next node ; Function to insert a node at the beginning of the Doubly Linked List ; allocate node ; put in the data ; since we are adding at the beginning , prev is always NULL ; link the old list off the new node ; change prev of head node to new node ; move the head to point to the new node ; Function to print nodes in a given doubly linked list ; if list is empty ; Driver program to test above ; Create the doubly linked list : 8 < -> 4 < -> 4 < -> 6 < -> 4 < -> 8 < -> 4 < -> 10 < -> 12 < -> 12 ; remove duplicate nodes
#include <bits/stdc++.h> NEW_LINE using namespace std ; struct Node { int data ; struct Node * next ; struct Node * prev ; } ; void deleteNode ( struct Node * * head_ref , struct Node * del ) { if ( * head_ref == NULL del == NULL ) return ; if ( * head_ref == del ) * head_ref = del -> next ; if ( del -> next != NULL ) del -> next -> prev = del -> prev ; if ( del -> prev != NULL ) del -> prev -> next = del -> next ; free ( del ) ; } void removeDuplicates ( struct Node * * head_ref ) { if ( ( * head_ref ) == NULL ) return ; unordered_set < int > us ; struct Node * current = * head_ref , * next ; while ( current != NULL ) { if ( us . find ( current -> data ) != us . end ( ) ) { next = current -> next ; deleteNode ( head_ref , current ) ; current = next ; } else { us . insert ( current -> data ) ; current = current -> next ; } } } void push ( struct Node * * head_ref , int new_data ) { struct Node * new_node = ( struct Node * ) malloc ( sizeof ( struct Node ) ) ; new_node -> data = new_data ; new_node -> prev = NULL ; new_node -> next = ( * head_ref ) ; if ( ( * head_ref ) != NULL ) ( * head_ref ) -> prev = new_node ; ( * head_ref ) = new_node ; } void printList ( struct Node * head ) { if ( head == NULL ) cout << " Doubly ▁ Linked ▁ list ▁ empty " ; while ( head != NULL ) { cout << head -> data << " ▁ " ; head = head -> next ; } } int main ( ) { struct Node * head = NULL ; push ( & head , 12 ) ; push ( & head , 12 ) ; push ( & head , 10 ) ; push ( & head , 4 ) ; push ( & head , 8 ) ; push ( & head , 4 ) ; push ( & head , 6 ) ; push ( & head , 4 ) ; push ( & head , 4 ) ; push ( & head , 8 ) ; cout << " Original ▁ Doubly ▁ linked ▁ list : n " ; printList ( head ) ; removeDuplicates ( & head ) ; cout << " Doubly linked list after " STRNEWLINE TABSYMBOL TABSYMBOL TABSYMBOL " removing duplicates : n " ; printList ( head ) ; return 0 ; }