Java Program For Sorting A Linked List Of 0s, 1s And 2s
Last Updated :
22 Dec, 2021
Given a linked list of 0s, 1s and 2s, sort it.
Examples:
Input: 1 -> 1 -> 2 -> 0 -> 2 -> 0 -> 1 -> NULL
Output: 0 -> 0 -> 1 -> 1 -> 1 -> 2 -> 2 -> NULL
Input: 1 -> 1 -> 2 -> 1 -> 0 -> NULLÂ
Output: 0 -> 1 -> 1 -> 1 -> 2 -> NULL
Source: Microsoft Interview | Set 1
Following steps can be used to sort the given linked list.
- Traverse the list and count the number of 0s, 1s, and 2s. Let the counts be n1, n2, and n3 respectively.
- Traverse the list again, fill the first n1 nodes with 0, then n2 nodes with 1, and finally n3 nodes with 2.
Below image is a dry run of the above approach:
Below is the implementation of the above approach:
Java
class LinkedList
{
Node head;
class Node
{
int data;
Node next;
Node( int d)
{
data = d;
next = null ;
}
}
void sortList()
{
int count[] = { 0 , 0 , 0 };
Node ptr = head;
while (ptr != null )
{
count[ptr.data]++;
ptr = ptr.next;
}
int i = 0 ;
ptr = head;
while (ptr != null )
{
if (count[i] == 0 )
i++;
else
{
ptr.data= i;
--count[i];
ptr = ptr.next;
}
}
}
public void push( int new_data)
{
Node new_node = new Node(new_data);
new_node.next = head;
head = new_node;
}
void printList()
{
Node temp = head;
while (temp != null )
{
System.out.print(temp.data + " " );
temp = temp.next;
}
System.out.println();
}
public static void main(String args[])
{
LinkedList llist = new LinkedList();
llist.push( 0 );
llist.push( 1 );
llist.push( 0 );
llist.push( 2 );
llist.push( 1 );
llist.push( 1 );
llist.push( 2 );
llist.push( 1 );
llist.push( 2 );
System.out.println(
"Linked List before sorting" );
llist.printList();
llist.sortList();
System.out.println(
"Linked List after sorting" );
llist.printList();
}
}
|
Output:Â
Linked List Before Sorting
2 1 2 1 1 2 0 1 0
Linked List After Sorting
0 0 1 1 1 1 2 2 2
Time Complexity: O(n) where n is the number of nodes in the linked list.Â
Auxiliary Space: O(1)
Please refer complete article on Sort a linked list of 0s, 1s and 2s for more details!
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