Check if each corresponding digit in two numbers sum to the same total?

Question

I'm brand new to C# and I've been absolutely stumped by a problem.

I'm trying to add each digit of a user input in a console app that are the same length (ex: Number 1 = 123 & Number 2 = 456). So I want to to check and see if 1+4=2+5=3+6 and then say if it's true or false.

My problem is, I don't know how to single out each individual digit that has been input. I feel like I'm absolutely overthinking this, but any help would be appreciated.

Answer 1

Let's solve the problem in general case and in the most accurate way. First we should answer two questions:

1. What shall we do with negative numbers? Just ignore the minus - or return false?
2. What if numbers have different lengths, e.g. 52 and 3? Shall we pad 3 to 03 (and thus return true) or return false?

Implementation

  public static bool Solution(int left, right) {
    // Comment this out (drop) if you accept negative numbers
    if (left < 0 || right < 0)
      return false;

    // Trim('-') - trimming '-' if we have negative numbers
    string A = left.ToString(CultureInfo.InvariantCulture).Trim('-');
    string B = right.ToString(CultureInfo.InvariantCulture).Trim('-');

    // Comment this out (drop) if you want to pad numbers with different lengths
    if (A.Length != B.Length)
      return false;

    // Padding with zeroes if required
    if (A.Length > B.Length)
      B = B.PadLeft(A.Length, '0');
    else if (B.Length > A.Length)
      A = A.PadLeft(B.Length, '0');

    // Finally, we can check
    for (int i = 1; i < A.Length; ++i)
      if (A[i] + B[i] != A[0] + B[0])
        return false; // Do we have a counter example?

    return true;   
  }      

Answer 2

You can use LINQ:

string number1 = "123";
string number2 = "456";

bool equalSums = number1
    .Zip(number2, (c1, c2) => Convert.ToInt32(c1) + Convert.ToInt32(c2))
    .Distinct()
    .Count() == 1;

Enumerable.Zip links two sequences via index, so char1 of first string is linked with char1 of other string and so on. Convert.ToInt32 converts the character to int and builds the sum of the two digits. Then Distinct removes duplicates and Count checks if there is only one number remaining which means all where equal.

Answer 3

This is a great problem to show the power of regex, assuming your numbers are stored in properties,

string num1 = Console.ReadLine();
string num2 = Console.ReadLine();

 int[] numbers1 = (from Match m in Regex.Matches(num1 , @"\d") select 
 int.Parse(m.Value)).ToArray();

 int[] numbers2 = (from Match m in Regex.Matches(num2 , @"\d") select int.Parse(m.Value)).ToArray();

Then you have two number arrays you can tests out e/g

if (numbers1[1] + numbers2[1] == numbers1[2] + numbers2[2])
{
Console.WriteLine("aye its true");
}
else {
//do something else
}

I hope that answers your question

P.S. I used Regex 101 for testing my regex, its a nice tool