Having trouble printing a series

December 17, 2021

Here’s the problem statement for what I’m supposed to do:

Write a program to print the following series up to the term input by user.
0, 1, 1, 2, 3, 5, 8, 13, ….
Where 0 is 1st term and 13 is 8th term.
Hint: 0, 1
0+1 = 1
0, 1, 1
1+1 = 2
0, 1, 1, 2

And here’s my code:

int prev_i = 0;


    cout << "Enter a number: " << endl;
    cin >> number;

    for (i = 0; i <= number; i++)
    {
        
        cout << prev_i + i << " ,";
        
        prev_i = i;
        
    }

I do get what is wrong with my code though. It adds i to prev_i then prev_i is set to i. So in the next iteration when i is 1 thats i + prev_i = 1 so now prev_i = 1 and here’s the problem i is 2 now so i + prev_i = 3. And I really can’t seem to figure out how to get 1 instead of 3 as the output here and so on.

Oh and don’t worry about i not declared properly. I just didn’t copy that part.

pls help!

>Solution :

You’re trying to generate a fibonacci sequence (starts with two terms (0,1), and each subsequent term is the addition of the prior two). Therefore, i should not be part of the calculation; it is only there to control looping.

A simple generation of the first ten numbers in the sequence is simply this:

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int a=0, b=1;
    for (int i=0; i<10; ++i)
    {
        printf("%d ", a);
        int c = a+b;
        a = b;
        b = c;
    }
    fputc('\n', stdout);

    return EXIT_SUCCESS;
}

That’s it. The code above will generate the following: