For loop creating an odd number at the beginning

[rooha88]

So I want to print even numbers in reverse from an integer that the user inputs. However, the first number that gets outputted is strange and I cannot understand why that number is getting outputted. This is my code:

#include <iostream>
using namespace std; 

int main ()
{  
    int N=0, i; 
    cout << "Enter N (an integer): " << endl; 
    cin >> N; 

    cout << "All even numbers " << N << "..0 = " << i;
    for (i= N; i>=0; i--) {
        if(i%2==0) {
            cout << i << " "; //Works but prints weird first number 
        }
    }
return 0; 
}

OUTPUT- for example 18 is integer entered:
All even numbers 18..0 = 3276618 16 14 12 10 8 6 4 2 0

EDIT: changing i=0 still outputs 018 14 12 10 8 6 4 2 0

[keskiverto]

int N=0, i;
cout << "Enter N (an integer): " << endl;
cin >> N;

cout << "All even numbers " << N << "..0 = " << i;

You print the value of i. What is its value?

[rooha88]

Well I want i to start at N and then go down to 0.

I entered i=0 at the top and this is what I get as the output:
018 16 14 12 10 8 6 4 2 0

[deleted account xyzzy]

PLEASE learn to use code tags, they make reading and commenting on source code MUCH easier.

http://www.cplusplus.com/articles/jEywvCM9/
http://www.cplusplus.com/articles/z13hAqkS/

HINT: you can edit your post and add code tags.

Some formatting & indentation would not hurt either

Before i is used in the for loop it is uninitialized, when you use in the std::cout statement before the for loop. You are getting whatever value is in i at the time. 0 (zero) with your compiler setup.

You can initialize i as part of the for loop:

#include <iostream>

int main()
{
   int N { };
   std::cout << "Enter N (an integer): ";
   std::cin >> N;

   std::cout << "All even numbers " << N << "..0 = ";

   for (int i { N }; i >= 0; --i) 
   {
      if (i % 2 == 0) 
      {
         std::cout << i << ' ';
      }
   }
   std::cout << '\n';
}

Enter N (an integer): 15
All even numbers 15..0 = 14 12 10 8 6 4 2 0

Another way to decrement values using an incrementing loop:

#include <iostream>

int main()
{
   int N { };
   std::cout << "Enter N (an integer): ";
   std::cin >> N;

   std::cout << "All even numbers " << N << "..0 = ";

   for (int i { }; i <= N; ++i) 
   {
      if ((N - i) % 2 == 0) 
      {
         std::cout << N - i << ' ';
      }
   }
   std::cout << '\n';
}

Enter N (an integer): 15
All even numbers 15..0 = 14 12 10 8 6 4 2 0

[keskiverto]

This cout << "All even numbers " << N << "..0 = " << i; could we written:

cout << "All even numbers ";
cout << N;
cout << "..0 = ";
cout << i; // Why do you print the i here, before the loop? 

[seeplus]

#include <iostream>

int main() {
	int N { };

	std::cout << "Enter N (a positive integer > 1): ";
	std::cin >> N;

	if (N < 2)
		return (std::cout << "Invalid integer\n"), 1;

	std::cout << "All even numbers " << N << "..0 = ";

	for (int i {N - (N % 2)}; i >= 0; i -= 2)
		std::cout << i << ' ';

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

[rooha88]

I tried using the first code @George P but it gives me this:

error: expected ';' at end of declaration
    int i { };

[jonnin]

just say int i = 0; then. or upgrade your compiler & be sure your flags are set to c++17 or better.

[deleted account xyzzy]

You are getting that error because you are not compiling as C++11 or better. The brackets are what is known as "uniform initialization."
https://mbevin.wordpress.com/2012/11/16/uniform-initialization/