Given a sorted linked list, delete all nodes that have duplicate numbers (all occurrences), leaving only numbers that appear once in the original list.
Examples:
Input: 23->28->28->35->49->49->53->53 Output: 23->35 Input: 11->11->11->11->75->75 Output: empty List
Note that this is different from Remove Duplicates From Linked List
The idea is to maintain a pointer (prev) to the node which just previous to the block of nodes we are checking for duplicates. In the first example, the pointer prev would point to 23 while we check for duplicates for node 28. Once we reach the last duplicate node with value 28 (name it current pointer), we can make the next field of prev node to be the next of current and update current=current.next. This would delete the block of nodes with value 28 which has duplicates.
// Java program to remove all occurrences of // duplicates from a sorted linked list // class to create Linked lIst class LinkedList{
// Head of linked list Node head = null ;
class Node
{ // Value in the node
int val;
Node next;
Node( int v)
{
// Default value of the next
// pointer field
val = v;
next = null ;
}
} // Function to insert data nodes into // the Linked List at the front public void insert( int data)
{ Node new_node = new Node(data);
new_node.next = head;
head = new_node;
} // Function to remove all occurrences // of duplicate elements public void removeAllDuplicates()
{ // Create a dummy node that acts like
// a fake head of list pointing to the
// original head
Node dummy = new Node( 0 );
// Dummy node points to the original head
dummy.next = head;
Node prev = dummy;
Node current = head;
while (current != null )
{
// Until the current and previous values
// are same, keep updating current
while (current.next != null &&
prev.next.val == current.next.val)
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
head = dummy.next;
} // Function to print the list elements public void printList()
{ Node trav = head;
if (head == null )
System.out.print( " List is empty" );
while (trav != null )
{
System.out.print(trav.val + " " );
trav = trav.next;
}
} // Driver code public static void main(String[] args)
{ LinkedList ll = new LinkedList();
ll.insert( 53 );
ll.insert( 53 );
ll.insert( 49 );
ll.insert( 49 );
ll.insert( 35 );
ll.insert( 28 );
ll.insert( 28 );
ll.insert( 23 );
System.out.println(
"Before removal of duplicates" );
ll.printList();
ll.removeAllDuplicates();
System.out.println(
"After removal of duplicates" );
ll.printList();
} } |
Output:
List before removal of duplicates 23 28 28 35 49 49 53 53 List after removal of duplicates 23 35
Time Complexity: O(n)
Please refer complete article on Remove all occurrences of duplicates from a sorted Linked List for more details!