Find the next fibonacci number

• Difficulty Level : Medium
• Last Updated : 10 Mar, 2021

Given a fibonacci number N, the task is to find the next fibonacci number.
Examples:

Input: N = 5
Output:
8 is the next fibonacci number after 5
Input: N = 3
Output:

Approach: The ratio of two adjacent numbers in the Fibonacci series rapidly approaches ((1 + sqrt(5)) / 2). So if N is multiplied by ((1 + sqrt(5)) / 2) and round it, the resultant number will be the next fibonacci number.
Below is the implementation of the above approach:

C++

 // C++ implementation of the approach#includeusing namespace std; // Function to return the next// fibonacci numberint nextFibonacci(int n){    double a = n * (1 + sqrt(5)) / 2.0;    return round(a);} // Driver codeint main(){    int n = 5;    cout << nextFibonacci(n);} // This code is contributed by mohit kumar 29

Java

 // Java implementation of the approachclass GFG{         // Function to return the next    // fibonacci number    static long nextFibonacci(int n)    {        double a = n * (1 + Math.sqrt(5)) / 2.0;        return Math.round(a);    }         // Driver code    public static void main (String[] args)    {        int n = 5;        System.out.println(nextFibonacci(n));    }} // This code is contributed by AnkitRai01

Python3

 # Python3 implementation of the approachfrom math import * # Function to return the next# fibonacci numberdef nextFibonacci(n):    a = n*(1 + sqrt(5))/2.0    return round(a) # Driver coden = 5print(nextFibonacci(n))

C#

 // C# implementation of the approachusing System; class GFG{         // Function to return the next    // fibonacci number    static long nextFibonacci(int n)    {        double a = n * (1 + Math.Sqrt(5)) / 2.0;        return (long)Math.Round(a);    }         // Driver code    public static void Main(String[] args)    {        int n = 5;        Console.WriteLine(nextFibonacci(n));    }} // This code is contributed by 29AjayKumar

Javascript


Output:
8

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