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Fibonacci number in an array

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  • Difficulty Level : Hard
  • Last Updated : 13 Jul, 2022
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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
Recommended Practice

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. 


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