Fibonacci number in an array

Last Updated : 19 Sep, 2023

We have been given an array and our task is to check if the element of array is present in Fibonacci series or not. If yes, then print that element.

Examples:

Input : 4, 2, 8, 5, 20, 1, 40, 13, 23
Output : 2 8 5 1 13
Here, Fibonacci series will be 0, 1, 1, 2, 
3, 5, 8, 13, 21, 34, 55. Numbers that are present 
in array are 2, 8, 5, 1, 13
For 2 -> 5 * 2 * 2  - 4 = 16
16 is a perfect square of 4

Input : 4, 7, 6, 25
Output : No Fibonacci number in this array

A number is said to be in Fibonacci series if either (5 * n * n - 4) or (5 * n * n + 4) is a perfect square. Please refer check if a given number is Fibonacci number for details.

Implementation:

C++

// CPP program to find Fibonacci series numbers 
// in a given array. 
#include <bits/stdc++.h> 
using namespace std; 

// Function to check number is a 
// perfect square or not 
bool isPerfectSquare(int num) 
{ 
    int n = sqrt(num); 
    return (n * n == num); 
} 

// Function to check if the number 
// is in Fibonacci or not 
void checkFib(int array[], int n) 
{ 
    int count = 0; 
    for (int i = 0; i < n; i++) { 
        if (isPerfectSquare(5 * array[i] * array[i] + 4) || isPerfectSquare(5 * array[i] * array[i] - 4)) { 
            cout << array[i] << " "; 
            count++; 
        } 
    } 
    if (count == 0) 
        cout << "None present" << endl; 
} 

// Driver function 
int main() 
{ 
    int array[] = { 4, 2, 8, 5, 20, 1, 40, 13, 23 }; 
    int n = sizeof(array) / sizeof(array[0]); 

    checkFib(array, n); 

    return 0; 
}

Java

// Java program to find Fibonacci series numbers
// in a given array
import java.io.*;
import java.math.*;

class GFG {
    // Function to check number is a
    // perfect square or not
    static boolean isPerfectSquare(int num)
    {
        int n = (int)(Math.sqrt(num));
        return (n * n == num);
    }

    // Function to check if the number
    // is in Fibonacci or not
    static void checkFib(int array[], int n)
    {
        int count = 0;
        for (int i = 0; i < n; i++) {
            if (isPerfectSquare(5 * array[i] * array[i] + 4) || isPerfectSquare(5 * array[i] * array[i] - 4)) {
                System.out.print(array[i] + " ");
                count++;
            }
        }
        if (count == 0)
            System.out.println("None Present");
    }

    // driver program
    public static void main(String[] args)
    {
        int array[] = { 4, 2, 8, 5, 20, 1, 40, 13, 23 };
        int n = array.length;
        checkFib(array, n);
    }
}

// Contributed by Pramod Kumar

Python3

# Python program to find
# Fibonacci series numbers
# in a given array.

import math

def isPerfectSquare(num):

    n = int(math.sqrt(num))
    return (n * n == num)

 
# Function to check if the number
# is in Fibonacci or not
def checkFib(array, n):

    count = 0
    for i in range(n):
    
        if (isPerfectSquare(5 * array[i] * array[i] + 4) or 
            isPerfectSquare(5 * array[i] * array[i] - 4)):
        
            print(array[i], " ", end ="");
            count = count + 1
        
    
    if (count == 0):
        print("None present");


# driver code
array = [4, 2, 8, 5, 20, 1, 40, 13, 23]
n = len(array)
 
checkFib(array, n)
 
# This code is contributed
# by Anant Agarwal.

// C# program to find Fibonacci series
// numbers in a given array
using System;

class GFG {
    
    // Function to check number is a
    // perfect square or not
    static bool isPerfectSquare(int num)
    {
        int n = (int)(Math.Sqrt(num));
        return (n * n == num);
    }

    // Function to check if the number
    // is in Fibonacci or not
    static void checkFib(int[] array, int n)
    {
        int count = 0;
        for (int i = 0; i < n; i++) {
            if (isPerfectSquare(5 * array[i] * array[i] + 4) ||
                isPerfectSquare(5 * array[i] * array[i] - 4)) 
            {
                Console.Write(array[i] + " ");
                count++;
            }
        }
        if (count == 0)
            Console.WriteLine("None Present");
    }

    // driver program
    public static void Main()
    {
        int[] array = { 4, 2, 8, 5, 20, 1, 40, 13, 23 };
        int n = array.Length;
        checkFib(array, n);
    }
}

// This code is contributed by Sam007

JavaScript

<script>
// Javascript program to find 
// Fibonacci series numbers 
// in a given array. 

// Function to check 
// number is a perfect 
// square or not 
function isPerfectSquare(num) 
{ 
    let n = parseInt(Math.sqrt(num)); 
    return (n * n == num); 
} 

// Function to check 
// if the number is 
// in Fibonacci or not 
function checkFib(array, n) 
{ 
    let count = 0; 
    for (let i = 0; i < n; i++) 
    { 
        if (isPerfectSquare(5 * array[i] * 
                                array[i] + 4) || 
            isPerfectSquare(5 * array[i] * 
                                array[i] - 4)) 
        { 
            document.write(array[i] + " "); 
            count++; 
        } 
    } 
    if (count == 0) 
        document.write("None present + <br>"); 
} 

// Driver Code 
let array = [4, 2, 8, 5, 20, 
                1, 40, 13, 23]; 
let n = array.length; 

checkFib(array, n); 

// This code is contributed by _saurabh_jaiswal
</script>

PHP

<?php
// PHP program to find 
// Fibonacci series numbers
// in a given array.

// Function to check 
// number is a perfect
// square or not
function isPerfectSquare($num)
{
    $n = (int)(sqrt($num));
    return ($n * $n == $num);
}

// Function to check 
// if the number is 
// in Fibonacci or not
function checkFib($array, $n)
{
    $count = 0;
    for ($i = 0; $i < $n; $i++) 
    {
        if (isPerfectSquare(5 * $array[$i] * 
                                $array[$i] + 4) || 
            isPerfectSquare(5 * $array[$i] * 
                                $array[$i] - 4)) 
        {
            echo $array[$i]." ";
            $count++;
        }
    }
    if ($count == 0)
        echo "None present\n";
}

// Driver Code
$array = array(4, 2, 8, 5, 20, 
                1, 40, 13, 23);
$n = sizeof($array);

checkFib($array, $n);

// This code is contributed by mits.

?>

Output

2 8 5 1 13

GCD and Fibonacci Numbers

Rishabh Jain

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Fibonacci number in an array

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