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Sum of all perfect numbers present in an Linked list
  • Last Updated : 18 Jun, 2021

Given an Linked list containing N positive integer, the task is to find the sum of all the perfect numbers from the list.
 

A number is perfect if is equal to the sum of its proper divisors i.e. the sum of its positive divisors excluding the number itself.

Examples: 
 

Input: L1 = 3 -> 6 -> 9 
Output:6 
Proper divisor sum of 3 = 1 
ans=0 
Proper divisor sum of 6 = 1 + 2 + 3 = 6 
ans=6; 
Proper divisor sum of 9 = 1 + 3 = 4 
ans=6;
Input: L1 = 17 -> 6 -> 10 -> 6 -> 4 
Output: 12 
 

 



Approach: Initialise sum = 0 and for every node of the list, find the sum of its proper divisors say sumFactors. If cur_node = sumFactors then update the resultant sum as sum = sum + cur_node. Print the sum in the end.
Below is the implementation of the above approach:
 

C++




// C++ implementation of the approach
 
#include <bits/stdc++.h>
using namespace std;
 
// Node of the singly linked list
struct Node {
    int data;
    Node* next;
};
 
// Function to insert a node
// at the beginning of
// the singly Linked List
void push(Node** head_ref, int new_data)
{
    // allocate node
    Node* new_node
        = (Node*)malloc(
            sizeof(struct Node));
 
    // put in the data
    new_node->data = new_data;
 
    // link the old list off the new node
    new_node->next = (*head_ref);
 
    // move the head to point
    // to the new node
    (*head_ref) = new_node;
}
// Function to return the sum of
// all the proper factors of n
int sumOfFactors(int n)
{
    int sum = 0;
    for (int f = 1; f <= n / 2; f++) {
 
        // f is the factor of n
        if (n % f == 0) {
            sum += f;
        }
    }
    return sum;
}
 
// Function to return the required sum
int getSum(Node* head_1)
{
 
    // To store the sum
    int sum = 0;
    Node* ptr = head_1;
    while (ptr != NULL) {
 
        // If current element is non-zero
        // and equal to the sum
        // of proper factors of itself
        if (ptr->data > 0
            && ptr->data
                   == sumOfFactors(ptr->data)) {
            sum += ptr->data;
        }
        ptr = ptr->next;
    }
    return sum;
}
 
// Driver code
int main()
{
    // start with the empty list
    Node* head1 = NULL;
 
    // create the linked list
    push(&head1, 17);
    push(&head1, 6);
    push(&head1, 10);
    push(&head1, 6);
    push(&head1, 4);
    int k = getSum(head1);
    cout << k;
    return 0;
}

Java




// Java implementation of the approach
class GFG{
 
// Node of the singly linked list
static class Node
{
    int data;
    Node next;
};
 
// Function to insert a node
// at the beginning of
// the singly Linked List
static Node push(Node head_ref,
                 int new_data)
{
     
    // Allocate node
    Node new_node= new Node();
 
    // Put in the data
    new_node.data = new_data;
 
    // Link the old list off the new node
    new_node.next = head_ref;
 
    // Move the head to point
    // to the new node
    head_ref = new_node;
     
    return head_ref;
}
 
// Function to return the sum of
// all the proper factors of n
static int sumOfFactors(int n)
{
    int sum = 0;
     
    for(int f = 1; f <= n / 2; f++)
    {
 
       // f is the factor of n
       if (n % f == 0)
       {
           sum += f;
       }
    }
    return sum;
}
 
// Function to return the required sum
static int getSum(Node head_1)
{
 
    // To store the sum
    int sum = 0;
     
    Node ptr = head_1;
     
    while (ptr != null)
    {
 
        // If current element is non-zero
        // and equal to the sum of proper
        //  factors of itself
        if (ptr.data > 0 && ptr.data ==
                sumOfFactors(ptr.data))
        {
            sum += ptr.data;
        }
        ptr = ptr.next;
    }
    return sum;
}
 
// Driver code
public static void main(String[] args)
{
     
    // Start with the empty list
    Node head = new Node();
 
    // Create the linked list
    head = push(head, 17);
    head = push(head, 6);
    head = push(head, 10);
    head = push(head, 6);
    head = push(head, 4);
     
    int k = getSum(head);
     
    System.out.print(k);
}
}
 
// This code is contributed by amal kumar choubey

Python3




# Python3 implementation of the approach
 
# Node class
class Node:
     
    # Function to initialize the node object
    def __init__(self, data):
        self.data = data
        self.next = None
     
# Linked List Class
class LinkedList:
 
    # Function to initialize the
    # LinkedList class.
    def __init__(self):
         
        self.head = None
 
    # This function insert a new node at
    # the beginning of the linked list
    def push(self, new_data):
     
        # Create a new Node
        new_node = Node(new_data)
 
        # Make next of new Node as head
        new_node.next = self.head
 
        # Move the head to point to new Node
        self.head = new_node
 
    # Function to return the required sum
    def getSum(self):
         
        # To store the sum
        Sum = 0
         
        # Initialising the pointer
        ptr = self.head
        while(True):
             
            # If current element is non Zero
            # and is a perfect number then
            # add to sum
            if(ptr.data > 0 and ptr.data ==
                   sumOfFactors(ptr.data)):
                Sum += ptr.data
 
            # Breaking the loop if list terminates
            if(ptr.next == None):
                break
 
            # Moving to next node
            ptr = ptr.next
 
        # Returning the sum
        return Sum
 
# Function to return the sum of
# all the proper factors of n
def sumOfFactors(n):
     
    Sum = 0
 
    # f is factor of n
    for f in range(1, (n // 2) + 1):
        if(n % f == 0):
            Sum += f
             
    return Sum
 
# Driver Code
if __name__=='__main__':
 
    # Start with empty list
    head1 = LinkedList()
 
    # Create the linked list
    head1.push(17)
    head1.push(6)
    head1.push(10)
    head1.push(6)
    head1.push(4)
 
    # Getting the required sum
    k = head1.getSum()
    print(k)
     
# This code is contributed by Amit Mangal

C#




// C# implementation of the approach
using System;
class GFG{
 
// Node of the singly linked list
class Node
{
    public int data;
    public Node next;
};
 
// Function to insert a node
// at the beginning of
// the singly Linked List
static Node push(Node head_ref,
                 int new_data)
{
     
    // Allocate node
    Node new_node= new Node();
 
    // Put in the data
    new_node.data = new_data;
 
    // Link the old list off the new node
    new_node.next = head_ref;
 
    // Move the head to point
    // to the new node
    head_ref = new_node;
     
    return head_ref;
}
 
// Function to return the sum of
// all the proper factors of n
static int sumOfFactors(int n)
{
    int sum = 0;
     
    for(int f = 1; f <= n / 2; f++)
    {
 
        // f is the factor of n
        if (n % f == 0)
        {
            sum += f;
        }
    }
    return sum;
}
 
// Function to return the required sum
static int getSum(Node head_1)
{
 
    // To store the sum
    int sum = 0;
     
    Node ptr = head_1;
     
    while (ptr != null)
    {
 
        // If current element is non-zero
        // and equal to the sum of proper
        // factors of itself
        if (ptr.data > 0 && ptr.data ==
               sumOfFactors(ptr.data))
        {
            sum += ptr.data;
        }
        ptr = ptr.next;
    }
    return sum;
}
 
// Driver code
public static void Main(String[] args)
{
     
    // Start with the empty list
    Node head = new Node();
 
    // Create the linked list
    head = push(head, 17);
    head = push(head, 6);
    head = push(head, 10);
    head = push(head, 6);
    head = push(head, 4);
     
    int k = getSum(head);
     
    Console.Write(k);
}
}
 
// This code is contributed by amal kumar choubey

Javascript




<script>
      // JavaScript implementation of the approach
      // Node of the singly linked list
      class Node {
        constructor() {
          this.data = 0;
          this.next = null;
        }
      }
 
      // Function to insert a node
      // at the beginning of
      // the singly Linked List
      function push(head_ref, new_data) {
        // Allocate node
        var new_node = new Node();
 
        // Put in the data
        new_node.data = new_data;
 
        // Link the old list off the new node
        new_node.next = head_ref;
 
        // Move the head to point
        // to the new node
        head_ref = new_node;
 
        return head_ref;
      }
 
      // Function to return the sum of
      // all the proper factors of n
      function sumOfFactors(n) {
        var sum = 0;
 
        for (var f = 1; f <= parseInt(n / 2); f++) {
          // f is the factor of n
          if (n % f == 0) {
            sum += f;
          }
        }
        return sum;
      }
 
      // Function to return the required sum
      function getSum(head_1) {
        // To store the sum
        var sum = 0;
 
        var ptr = head_1;
 
        while (ptr != null) {
          // If current element is non-zero
          // and equal to the sum of proper
          // factors of itself
          if (ptr.data > 0 && ptr.data == sumOfFactors(ptr.data)) {
            sum += ptr.data;
          }
          ptr = ptr.next;
        }
        return sum;
      }
 
      // Driver code
      // Start with the empty list
      var head = new Node();
 
      // Create the linked list
      head = push(head, 17);
      head = push(head, 6);
      head = push(head, 10);
      head = push(head, 6);
      head = push(head, 4);
 
      var k = getSum(head);
 
      document.write(k);
       
      // This code is contributed by rdtank.
    </script>
Output: 
12

 

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