Replace every node in linked list with its closest fibonacci number

Given a singly linked list of integers, the task is to replace every node with its closest Fibonacci number and return the modified linked list.

Examples:

Input: List: 3->5->9->12->13->15->null
Output: 3->5->8->13->13->13->null
Explanation: The closest Fibonacci numbers for each node are:

• Node 1 (value = 3): Closest Fibonacci number = 3.
• Node 2 (value = 5): Closest Fibonacci number = 5.
• Node 3 (value = 9): Closest Fibonacci number = 8.
• Node 4 (value = 12): Closest Fibonacci number = 13.
• Node 5 (value = 13): Closest Fibonacci number = 13.
• Node 6 (value = 15): Closest Fibonacci number = 13.
     

Input: List : 1->2->3->4->5->null
Output: 1->2->3->5->5->null
Explanation: The closest Fibonacci numbers for each node are:

• Node 1 (value = 1): Closest Fibonacci number = 1.
• Node 2 (value = 2): Closest Fibonacci number = 2.
• Node 3 (value = 3): Closest Fibonacci number = 3.
• Node 4 (value = 4): Closest Fibonacci number = 5.
• Node 5 (value = 5): Closest Fibonacci number = 5.

Approach: This can be solved with the following idea:

This problem requires us to modify a linked list such that each node is replaced with its closest Fibonacci number. To solve this problem, we can start by creating an array of Fibonacci numbers that are greater than the maximum value in the linked list. We can then iterate over each node in the linked list, finding the closest Fibonacci number using the array we created.

Below are the steps for the above idea:

• Define a function getClosestFibonacci() that takes an integer n and a vector fib as input.
• Define an integer variable i and set it to 0.
• While the ith Fibonacci number in fib is less than n, increment i.
• If the ith Fibonacci number in fib is equal to n or if i is 0, return n.
• Otherwise, if n is closer to the i-1th Fibonacci number than the ith Fibonacci number, return the i-1th Fibonacci number. Otherwise, return the ith Fibonacci number.
• Define a function replaceWithClosestFibonacci() that takes a linked list head as input.
• Create a vector fib that contains all the Fibonacci numbers up to a certain limit. We can start by adding 0 and 1 to the vector, and then use a loop to generate additional Fibonacci numbers until we reach a limit (e.g., 1000000).
• Define a pointer curr and set it to head.
• While curr is not null, set the value of curr to the closest Fibonacci number using getClosestFibonacci() and the fib vector, and move to curr to the next node in the linked list.
• Return the modified linked list head.

Below is the implementation of the above approach:

// C++ Implementation
#include <iostream>
#include <vector>
using namespace std;

// Structure of Node
struct Node {
    int val;
    Node* next;
    Node(int v)
        : val(v), next(nullptr)
    {
    }
};

// Function to find closest fibonacci
// Number
int getClosestFibonacci(int n, vector<int>& fib)
{
    int i = 0;
    while (fib[i] < n) {
        i++;
    }
    if (fib[i] == n || i == 0) {
        return n;
    }
    else {
        return (n - fib[i - 1] < fib[i] - n) ? fib[i - 1]
                                             : fib[i];
    }
}

// Function to replace node value with
// closest number
Node* replaceWithClosestFibonacci(Node* head)
{
    vector<int> fib;
    fib.push_back(0);
    fib.push_back(1);
    int fibNum = 1;

    // set a limit for largest
    // Fibonacci number
    while (fibNum <= 1000000) {
        fib.push_back(fibNum);
        fibNum = fib[fib.size() - 1] + fib[fib.size() - 2];
    }

    Node* curr = head;
    while (curr != nullptr) {
        curr->val = getClosestFibonacci(curr->val, fib);
        curr = curr->next;
    }
    return head;
}

// Function to print list
void printList(Node* head)
{
    Node* curr = head;
    while (curr != nullptr) {
        cout << curr->val << "->";
        curr = curr->next;
    }
    cout << "null" << endl;
}

// Driver code
int main()
{
    Node* head = new Node(3);
    head->next = new Node(5);
    head->next->next = new Node(9);
    head->next->next->next = new Node(12);
    head->next->next->next->next = new Node(13);
    head->next->next->next->next->next = new Node(15);

    // Function call
    head = replaceWithClosestFibonacci(head);

    printList(head);

    return 0;
}

// Java Implementation

import java.util.ArrayList;
import java.util.List;

// Structure of Node
class Node {
    int val;
    Node next;

    Node(int v) {
        val = v;
        next = null;
    }
}

public class Main {

    // Function to find closest fibonacci Number
    static int getClosestFibonacci(int n, List<Integer> fib) {
        int i = 0;
        while (fib.get(i) < n) {
            i++;
        }
        if (fib.get(i) == n || i == 0) {
            return n;
        } else {
            return (n - fib.get(i - 1) < fib.get(i) - n) ? 
                    fib.get(i - 1) : fib.get(i);
        }
    }

    // Function to replace node value with closest number
    static Node replaceWithClosestFibonacci(Node head) {
        List<Integer> fib = new ArrayList<>();
        fib.add(0);
        fib.add(1);
        int fibNum = 1;

        // set a limit for largest Fibonacci number
        while (fibNum <= 1000000) {
            fib.add(fibNum);
            fibNum = fib.get(fib.size() - 1) + 
                     fib.get(fib.size() - 2);
        }

        Node curr = head;
        while (curr != null) {
            curr.val = getClosestFibonacci(curr.val, fib);
            curr = curr.next;
        }
        return head;
    }

    // Function to print list
    static void printList(Node head) {
        Node curr = head;
        while (curr != null) {
            System.out.print(curr.val + "->");
            curr = curr.next;
        }
        System.out.println("null");
    }

    // Driver code
    public static void main(String[] args) {
        Node head = new Node(3);
        head.next = new Node(5);
        head.next.next = new Node(9);
        head.next.next.next = new Node(12);
        head.next.next.next.next = new Node(13);
        head.next.next.next.next.next = new Node(15);

        // Function call
        head = replaceWithClosestFibonacci(head);

        printList(head);
    }
}

# Python3 Implementation
import math

# Structure of Node


class Node:
    def __init__(self, v):
        self.val = v
        self.next = None

# Function to find closest fibonacci
# Number


def getClosestFibonacci(n, fib):
    i = 0
    while fib[i] < n:
        i += 1
    if fib[i] == n or i == 0:
        return n
    else:
        return fib[i - 1] if (n - fib[i - 1] < fib[i] - n) else fib[i]

# Function to replace node value with
# closest number


def replaceWithClosestFibonacci(head):
    fib = [0, 1]
    fibNum = 1

    # set a limit for largest
    # Fibonacci number
    while fibNum <= 1000000:
        fib.append(fibNum)
        fibNum = fib[-1] + fib[-2]

    curr = head
    while curr != None:
        curr.val = getClosestFibonacci(curr.val, fib)
        curr = curr.next
    return head

# Function to print list


def printList(head):
    curr = head
    while curr != None:
        print(curr.val, end="->")
        curr = curr.next
    print("null")


# Driver code
if __name__ == '__main__':
    head = Node(3)
    head.next = Node(5)
    head.next.next = Node(9)
    head.next.next.next = Node(12)
    head.next.next.next.next = Node(13)
    head.next.next.next.next.next = Node(15)

    # Function call
    head = replaceWithClosestFibonacci(head)

    printList(head)

//using c# approach

using System;
using System.Collections.Generic;

// Structure of Node
public class Node
{
    public int val;
    public Node next;

    public Node(int v)
    {
        val = v;
        next = null;
    }
}

public class GFG
{
    // Function to find closest fibonacci number
    public static int GetClosestFibonacci(int n, List<int> fib)
    {
        int i = 0;
        while (fib[i] < n)
        {
            i++;
        }
        if (fib[i] == n || i == 0)
        {
            return n;
        }
        else
        {
            return (n - fib[i - 1] < fib[i] - n) ? fib[i - 1] : fib[i];
        }
    }

    // Function to replace node value with the closest fibonacci number
    public static Node ReplaceWithClosestFibonacci(Node head)
    {
        List<int> fib = new List<int> { 0, 1 };
        int fibNum = 1;

        // Set a limit for the largest Fibonacci number
        while (fibNum <= 1000000)
        {
            fib.Add(fibNum);
            fibNum = fib[fib.Count - 1] + fib[fib.Count - 2];
        }

        Node curr = head;
        while (curr != null)
        {
            curr.val = GetClosestFibonacci(curr.val, fib);
            curr = curr.next;
        }
        return head;
    }

    // Function to print the list
    public static void PrintList(Node head)
    {
        Node curr = head;
        while (curr != null)
        {
            Console.Write(curr.val + "->");
            curr = curr.next;
        }
        Console.WriteLine("null");
    }

    // Driver code
    public static void Main()
    {
        Node head = new Node(3);
        head.next = new Node(5);
        head.next.next = new Node(9);
        head.next.next.next = new Node(12);
        head.next.next.next.next = new Node(13);
        head.next.next.next.next.next = new Node(15);

        // Function call
        head = ReplaceWithClosestFibonacci(head);

        PrintList(head);
    }
}

// Structure of Node
class Node {
    constructor(v) {
        this.val = v;
        this.next = null;
    }
}

// Function to find closest fibonacci Number
function getClosestFibonacci(n, fib) {
    let i = 0;
    while (fib[i] < n) {
        i++;
    }
    if (fib[i] === n || i === 0) {
        return n;
    } else {
        return (n - fib[i - 1] < fib[i] - n) ?
            fib[i - 1] : fib[i];
    }
}

// Function to replace node value with closest number
function replaceWithClosestFibonacci(head) {
    const fib = [0, 1];
    let fibNum = 1;

    // set a limit for the largest Fibonacci number
    while (fibNum <= 1000000) {
        fib.push(fibNum);
        fibNum = fib[fib.length - 1] +
            fib[fib.length - 2];
    }

    let curr = head;
    while (curr !== null) {
        curr.val = getClosestFibonacci(curr.val, fib);
        curr = curr.next;
    }
    return head;
}

// Function to print list
function printList(head) {
    let curr = head;
    while (curr !== null) {
        console.log(curr.val + "->");
        curr = curr.next;
    }
    console.log("null");
}

// Node class is defined above

// Driver code
    const head = new Node(3);
    head.next = new Node(5);
    head.next.next = new Node(9);
    head.next.next.next = new Node(12);
    head.next.next.next.next = new Node(13);
    head.next.next.next.next.next = new Node(15);

    // Function call
    replaceWithClosestFibonacci(head);

    printList(head);

3->5->8->13->13->13->null

Time Complexity: O(n*logn)
Auxiliary Space: O(k)