How to display for each digit, starting with the most significant, whether it is odd or even-CodePudding

I am like 2 weeks new to C# or coding overall and I am trying to figure out the following:

Write a console application that displays for each digit, starting with the most significant, whether it is odd or even.

For input data:

5228

The console will display:

ODD
EVEN
EVEN
EVEN

When running my code I get:

EVEN
EVEN
EVEN
ODD

Can you help me start from the most significant digit?

This is my current implementation:

using System;
public class TestVariablesandExpressions
{

    static void Main(string[] args)
    {
        string inputData = Console.ReadLine();
        int num = Convert.ToInt32(inputData);
        int reverse = 0;

        while (num > 0)
        {
            reverse = reverse * 10   num % 10;
            num /= 10;

      

            if (reverse % 2 == 0)
            {
                Console.WriteLine("EVEN");
            }
            else
            {
                Console.WriteLine("ODD");
            }
        }      
    }
}

CodePudding user response：

Sorry, but you can't solve the task with you current reverse implementation: the counter example is when num ends with 0:

num == 12000 => (reverse) => 00012 == 12 => "ODD EVEN"

Another problem which is in you current code is a potential integer overflow: no int value can be greater than int.MaxValue = 2147483647, but if num ends with 2..9 the reversed value can exceed the int.MaxValue:

1000000009 => (reverse) => 9000000001 => (overflow) == 410065409 
(or something else depending on reverse implementation)

But you can preserve trailing zeroes and forget about overflow by using string instead of int. The only potential problem is negative numbers where we should skip - (-123 => ODD EVEN ODD).

int num = ...

string text = num.ToString(); 

for (int i = 0; i < text.Length;   i)
  if (text[i] >= '0' && text[i] <= '9') { // In case we have negative numbers
    if ((text[i] - '0') % 2 == 0) // Note, that text[i] is char, not int
      Console.WriteLine("EVEN");
    else
      Console.WriteLine("ODD");
  }

CodePudding user response：

Modulo operator % returns the last digit. It would be way easier to handle a string, so you can use foreach loop over each character, then convert it to an integer in your loop.

First control if the entry is a number, and trim spaces with Convert.ToInt32(inputData).ToString(); (It converts it to a number, then converts the number to a string)

string inputData = Console.ReadLine();
inputData = Convert.ToInt32(inputData).ToString();
foreach (char digit in inputData)
{
    if (Convert.ToInt32(digit.ToString()) % 2 == 0)
    {
        Console.WriteLine("EVEN");
    }
    else
    {
        Console.WriteLine("ODD");
    }
}

Or shorter :

string inputData = Console.ReadLine();
inputData = Convert.ToInt32(inputData).ToString();
foreach (char digit in inputData)
{
    Console.WriteLine(Convert.ToInt32(digit.ToString()) % 2 == 0 ? "EVEN" : "ODD");
}