Fibonacci number in an array

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 = 36
36 is a perfect square root of 6.

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#

// 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

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.

?>

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>

Output

2 8 5 1 13 

This article is contributed by Rishabh Jain. If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.