Question

In C++

Implement the function is fibonacci.array that takes an array of inte- gers and its size as input. The goal of the function is to return true if every element in the array is a Fibonacci number, false otherwise. You do not need to change the main function.

#include<iostream>
using namespace std;

//Implement the function below.

bool is_fibonacci_array(int*,int);

//Param 1: pointer to the beginning of an array of integers
//Param 2: size of that array
//Returns: true, is every element in the input array is a Fibonacci number
                //(the order of the numbers in the array need not be ordered
                //as per the Fibonacci sequence)
        //false, otherwise

//A Fibonacci sequence is generated as follows.
//The first two numbers in the sequence are 0 and 1.
//The following numbers in the sequence are calculated by adding
//the previous two numbers in the sequence. Thus the third number in the
//sequence would be 1 (i.e., 0+1), the fourth being 2 (i.e., 1+1), the
//fifth being 3 (i.e., 1+2), and so on, giving the following sequence:
//0, 1, 1, 2, 3, 5, 8, 13, 21, 34, etc.

int main(){
  //this is a Fibonacci array
  int a[5]={317811,28657,75025,3,8};
  //this is NOT a Fibonacci array
  int b[3]={0,1,4};

  int flag=is_fibonacci_array(a,5);

  //should print "Is a Fibonacci array."
  if (flag)
    cout << "Is a Fibonacci array.\n";
  else
    cout << "Is not a Fibonacci array.\n";

  flag=is_fibonacci_array(b,3);

  //should print "Is not a Fibonacci array."
  if (flag)
    cout << "Is a Fibonacci array.\n";
  else
    cout << "Is not a Fibonacci array.\n";
}

Answer 1

Program :

#include <iostream>

#include <math.h>

using namespace std;

// Its an utility function which returns true if x is a perfect square

bool isPerfectSquare(int x)

{

int s = sqrt(x);

return (s*s == x);

}

// Its an utility function which returns true if n is a Fibonacci Number, else false

bool is_fibonacci_array(int inputArray[] , int size)

{

bool flag;

// n is Fibonacci if one of (5*n*n + 4) or (5*n*n - 4) or both is a perferct square

for(int j=0; j < size; j++){

int n = inputArray[j];

flag = isPerfectSquare(5*n*n + 4) ||

isPerfectSquare(5*n*n - 4);

if(!flag){

break;

}

}

return flag;

}

// main function where program starts

int main()

{

int size;

// asking user to enter the size of array

cout << "Enter the size of array" << endl;

// storing entered size in size variable of int type

cin >> size;

int inputArray[size];

// asking user to enter array values and storing them in inputArray of type int

for(int i=0; i<size; i++)

{

cout << "Value of inputArray[" << i << "] : " << endl;

cin >> inputArray[i];

}

  

// calling is_fibonacci_array and storing result in output of boolean type

bool output = is_fibonacci_array(inputArray, size);

// printing whether entered array is fibonacci or not.

if(output)

cout << "Is a Fibonacci array. \n" << endl;

else

cout << "Is not a Fibonacci array.\n";

return 0;

}

sample input and output :

Program snapshot :

I have divided the whole program into 2 parts since its very big in no. of lines.