Im trying to create a a code that count numbers divisible by 9 by putting numbers into an array and count the numbers in it [closed]

Question

Im trying to create a a code that count numbers divisible by 9 by putting numbers into an array and count the numbers in it but it only prints 1 instead of the number of numbers divisible by 9 please help me i want to use array to count those numbers

#include <iostream>
using namespace std;
int main(){
    int a,b,i;
    int numbers[]={i};
    cin >>a>>b;
    for (i=a; i<=b; i++)
        if (i%9==0){
            cout << sizeof(numbers)/sizeof(numbers[0]);
        }        
}

Answer 1

This declaration

int numbers[]={i};

declares an array with only one element and initializes it with an indeterminate value stored in the variable i because the variable i was not initialized.

The body of this if statement

    if (i%9==0){
        cout << sizeof(numbers)/sizeof(numbers[0]);
    }

does not make a sense because it always outputs the number of elements in the array numbers that has only one element. But according to the description of the assignment you have to place numbers divisible by 9 into the array.

As the user can enter arbitrary values for the variables a and b then it means that you need a variable length array. However variable length arrays is not a standard C++ feature. Instead you should use the standard container std::vector.

The program can look the following way

#include <iostream>
#include <vector>
#include <utility>

int main()
{
    int a = 0, b = 0;
    std::vector<int> numbers;

    const int divisor = 9; 

    std::cout << "Enter two integer numbers: ";
    std::cin >> a >> b;

    if ( b < a ) std::swap( a, b );

    for ( int i = a; not ( b < i ); ++i )
    {
        if ( i % divisor == 0 ) numbers.push_back( i );
    }

    std::cout << "There are " << numbers.size() 
              << " numbers divisible by " << divisor
              << " in the range [" << a << ", " << b << "]\n";

    if ( numbers.size() != 0 )
    {
        std::cout << "They are ";

        for ( const auto &n : numbers )
        {
            std::cout << n << ' ';
        }

        std::cout << '\n';
    } 
}

Answer 2

Your code is printing one's for each element found because your array only has one element in it!

Print i instead like so:

#include <iostream>
using namespace std;
int main(){
    int a,b,i;
    //int numbers[]={i};
    cin >>a>>b;
    for (i=a; i<=b; i++)
    {
        if (i%9==0)
        {
            cout << "i: " << i << endl;
        }
    }
}