Replace each node with its Surpasser Count in Linked List

Given LinkedList, replace each node’s value with its surpasser count. That is the count of elements which are greater towards its right.

Examples:

Input : 10->12->5->40->21->70->1->49->37->NULL
Output : 6->5->5->2->3->0->2->0->0->NULL
Explanation :
Element in the first node is 10 and the number of elements to the right of the node that are greater than 10 is 6. Therefore replace the node with 6.
Element in the first node is 12 and the number of elements to the right of the node that are greater than 12 is 5. Therefore replace the node with 5.
Similarly, replace for all the elements in the list.

Input : 5->4->6->3->2->NULL
Output : 1->1->0->0->0->NULL

Simple Approach

  1. Take two pointers p and x. The pointer p is used to traverse the list and x is used to traverse the right half of the list for every node.
  2. Initialize a variable count to count the nodes greater than the current nodes.
  3. Traverse through all the nodes in the list using the pointer p.
    • Initialize the count to 0.
    • Initialize the pointer x to point the current node p.
    • Count the number of nodes that are greater than the current node.
    • Replace the current node with the count.
  4. Repeat step 4 until the list is traversed completely.

Below is the implementation of the above approach:

C++

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// C++ program to replace the nodes
// with their surpasser count
  
#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
Node* newNode(int data)
{
    Node* temp = new Node;
    temp->data = data;
    temp->next = NULL;
  
    return temp;
}
  
// Function to display the linked list
void printList(Node* node)
{
    while (node != NULL) {
  
        cout << node->data << " ";
  
        node = node->next;
    }
}
  
// Function to check Surpasser Count
void replaceNodes(Node* head)
{
    // Pointer used to traverse through
    // all the nodes in the list
    Node* p = head;
  
    // Pointer used to traverse through the right
    // elements to count the greater elements
    Node* x = NULL;
  
    // Variable to count the number of
    // elements greater than the
    // current element on right
    int count = 0;
  
    int i;
  
    // Traverse through all the elements
    // in the list
    while (p != NULL) {
  
        count = 0;
  
        i = 0;
  
        // Initialize x to current node
        x = p;
  
        // Check or count the number of nodes
        // that are greater than the current
        // node on right
        while (x != NULL) {
  
            if (x->data > p->data)
                count++;
  
            x = x->next;
        }
  
        // Replace the node data with the
        // count of elements greater than
        // the current element
        p->data = count;
        p = p->next;
    }
}
  
// Driver code
int main()
{
    // Creating the linked list
    Node* head = newNode(10);
    head->next = newNode(12);
    head->next->next = newNode(5);
    head->next->next->next = newNode(40);
    head->next->next->next->next = newNode(21);
    head->next->next->next->next->next = newNode(70);
    head->next->next->next->next->next->next = newNode(1);
    head->next->next->next->next->next->next->next = newNode(49);
    head->next->next->next->next->next->next->next->next = newNode(37);
  
    replaceNodes(head);
  
    printList(head);
  
    return 0;
}

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Java

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// Java program to replace the nodes
// with their surpasser count
  
class GFG {
  
// A linked list node
static class Node {
    int data;
    Node next;
};
   
// Utility function to create a new Node
static Node newNode(int data)
{
    Node temp = new Node();
    temp.data = data;
    temp.next = null;
   
    return temp;
}
   
// Function to display the linked list
static void printList(Node node)
{
    while (node != null) {
        System.out.print(node.data+" ");
   
        node = node.next;
    }
}
   
// Function to check Surpasser Count
static void replaceNodes(Node head)
{
    // Pointer used to traverse through
    // all the nodes in the list
    Node p = head;
   
    // Pointer used to traverse through the right
    // elements to count the greater elements
    Node x = null;
   
    // Variable to count the number of
    // elements greater than the
    // current element on right
    int count = 0;
   
    int i;
   
    // Traverse through all the elements
    // in the list
    while (p != null) {
   
        count = 0;
   
        i = 0;
   
        // Initialize x to current node
        x = p;
   
        // Check or count the number of nodes
        // that are greater than the current
        // node on right
        while (x != null) {
   
            if (x.data > p.data)
                count++;
   
            x = x.next;
        }
   
        // Replace the node data with the
        // count of elements greater than
        // the current element
        p.data = count;
        p = p.next;
    }
}
   
// Driver code
public static void main(String[] args) {
  // Creating the linked list
    Node head = newNode(10);
    head.next = newNode(12);
    head.next.next = newNode(5);
    head.next.next.next = newNode(40);
    head.next.next.next.next = newNode(21);
    head.next.next.next.next.next = newNode(70);
    head.next.next.next.next.next.next = newNode(1);
    head.next.next.next.next.next.next.next = newNode(49);
    head.next.next.next.next.next.next.next.next = newNode(37);
   
    replaceNodes(head);
   
    printList(head);
    }
}
  
// This code has been contributed by 29AjayKumar

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Python3

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# Python3 program to replace the nodes 
# with their surpasser count 
  
# A linked list node 
class Node:
      
    def __init__(self, data):
        self.data = data 
        self.next = None
  
# Function to display the linked list 
def printList(node): 
  
    while node != None
        print(node.data, end = " "
        node = node.next
      
# Function to check Surpasser Count 
def replaceNodes(head): 
  
    # Pointer used to traverse through 
    # all the nodes in the list 
    p = head 
  
    # Pointer used to traverse through
    # the right elements to count the 
    # greater elements 
    x = None
  
    # Variable to count the number of 
    # elements greater than the 
    # current element on right 
    count = 0
  
    # Traverse through all the elements 
    # in the list 
    while p != None
  
        count = 0
  
        # Initialize x to current node 
        x =
  
        # Check or count the number of nodes 
        # that are greater than the current 
        # node on right 
        while x != None
  
            if x.data > p.data: 
                count += 1
  
            x = x.next
  
        # Replace the node data with the 
        # count of elements greater than 
        # the current element 
        p.data = count 
        p = p.next
  
# Driver code 
if __name__ == "__main__":
  
    # Creating the linked list 
    head = Node(10
    head.next = Node(12
    head.next.next = Node(5
    head.next.next.next = Node(40
    head.next.next.next.next = Node(21
    head.next.next.next.next.next = Node(70
    head.next.next.next.next.next.next = Node(1
    head.next.next.next.next.next.next.next = Node(49
    head.next.next.next.next.next.next.next.next = Node(37
  
    replaceNodes(head) 
  
    printList(head) 
  
# This code is contributed by Rituraj Jain

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C#

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// C# program to replace the nodes
// with their surpasser count
using System;
  
class GFG 
{
  
// A linked list node
public class Node
{
    public int data;
    public Node next;
};
  
// Utility function to create a new Node
static Node newNode(int data)
{
    Node temp = new Node();
    temp.data = data;
    temp.next = null;
  
    return temp;
}
  
// Function to display the linked list
static void printList(Node node)
{
    while (node != null
    {
        Console.Write(node.data + " ");
  
        node = node.next;
    }
}
  
// Function to check Surpasser Count
static void replaceNodes(Node head)
{
    // Pointer used to traverse through
    // all the nodes in the list
    Node p = head;
  
    // Pointer used to traverse through the right
    // elements to count the greater elements
    Node x = null;
  
    // Variable to count the number of
    // elements greater than the
    // current element on right
    int count = 0;
  
    int i;
  
    // Traverse through all the elements
    // in the list
    while (p != null
    {
  
        count = 0;
  
        i = 0;
  
        // Initialize x to current node
        x = p;
  
        // Check or count the number of nodes
        // that are greater than the current
        // node on right
        while (x != null
        {
  
            if (x.data > p.data)
                count++;
  
            x = x.next;
        }
  
        // Replace the node data with the
        // count of elements greater than
        // the current element
        p.data = count;
        p = p.next;
    }
}
  
// Driver code
public static void Main() 
{
    // Creating the linked list
    Node head = newNode(10);
    head.next = newNode(12);
    head.next.next = newNode(5);
    head.next.next.next = newNode(40);
    head.next.next.next.next = newNode(21);
    head.next.next.next.next.next = newNode(70);
    head.next.next.next.next.next.next = newNode(1);
    head.next.next.next.next.next.next.next = newNode(49);
    head.next.next.next.next.next.next.next.next = newNode(37);
  
    replaceNodes(head);
  
    printList(head);
}
}
  
/* This code contributed by PrinciRaj1992 */

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Output:

6 5 5 2 3 0 2 0 0

Time Complexity: O(N2) where N is the number of nodes in the linked list.
Auxiliary Space: O(1)



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