Trying to figure out a method

Shaker AlSalem

A palindrome is a number or a text phrase that reads the same backwards as forwards. For example, each of the following five-digit integers is a palindrome: 12321, 55555, 45554 and 11611. Write a program that reads in a five-digit integer and determines whether it is a palindrome. [Hint: Use the division and modulus operators to separate the number into its individual digits.] Note: Although this exercise talks about a five digit number, think about any length for the number.

im not sure whats the method required here, im guessing it has to be divided by 10 or something, but how do you apply that on C#.
Thanks!

3 Replies

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Vulpes14y ago
Accepted answer
Well, I'd certainly use Frogleg's method in practice but I think what you're supposed to do is something like this which (as you surmised) does involve repeated division by 10 and finding the remainder:

using System;

class Program
{
static void Main()
{
int number = 0;

while(true)
{
Console.Write("Please enter a five digit number or q to quit : ");
string input = Console.ReadLine();

if(input.Length > 0 && input.ToLower()[0] == 'q')
{
return;
}
else if(input.Length != 5)
{
Console.WriteLine("Needs to be exactly five digits");
}
else if(!int.TryParse(input, out number))
{
Console.WriteLine("Not a valid number");
}
else
{
bool isPalindrome = IsPalindrome(number);
if (isPalindrome)
Console.WriteLine("{0:D5} is a palindrome", number);
else
Console.WriteLine("{0:D5} is not a palindrome", number);
Console.WriteLine();
}
}
}

static bool IsPalindrome(int number)
{
int[] digits = new int[5];
int index = 4;
while(index >= 0)
{
digits[index] = number % 10;
number /= 10;
index--;
}

if (digits[0] == digits[4] && digits[1] == digits[3]) return true;
return false;
}

}
Shaker AlSalem14y ago
Much appreciated, thanks a lot guys!!
Frogleg14y ago
Since I used a textbox to enter the numbers, I left them as a string - you can convert them to integers as you need

public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}

private void Form1_Load(object sender, EventArgs e)
{

}

private void button1_Click(object sender, EventArgs e)
{
string ss = textBox1.Text;

string str = ReverseString(ss);

if (str == ss)
{
MessageBox.Show("Palindrone");
}
else
{
MessageBox.Show("Not a Palindrone");
}

}

public string ReverseString(string s)
{
char[] arr = s.ToCharArray();
Array.Reverse(arr);
return new string(arr);
}

}