C# Program to Read a String and Find the Sum of all Digits

C# is a popular object-oriented programming language used to develop Windows applications, web applications, and games. In this article, we will discuss how to write a C# program to read a string and find the sum of all digits present in the string.

Approach

To find the sum of digits in a string, we need to iterate through each character, check if it's a digit using char.IsDigit(), and convert it to an integer to add to our running sum.

Using char.IsDigit() Method

The char.IsDigit() method determines whether a character represents a decimal digit. Here's the complete program

using System;

class Program {
   static void Main(string[] args) {
      string inputString = "Hello123World456";
      int sum = 0;
      
      Console.WriteLine("Input string: " + inputString);
      
      foreach (char c in inputString) {
         if (char.IsDigit(c)) {
            sum += int.Parse(c.ToString());
            Console.WriteLine("Found digit: " + c);
         }
      }
      
      Console.WriteLine("The sum of digits in the string is: " + sum);
   }
}

The output of the above code is

Input string: Hello123World456
Found digit: 1
Found digit: 2
Found digit: 3
Found digit: 4
Found digit: 5
Found digit: 6
The sum of digits in the string is: 21

Using Character Arithmetic

An alternative approach is to use character arithmetic by subtracting '0' from the digit character

using System;

class Program {
   static void Main(string[] args) {
      string inputString = "ABC789XYZ";
      int sum = 0;
      
      Console.WriteLine("Input string: " + inputString);
      
      foreach (char c in inputString) {
         if (char.IsDigit(c)) {
            sum += c - '0';  // Convert char to int using ASCII arithmetic
         }
      }
      
      Console.WriteLine("Sum of all digits: " + sum);
   }
}

The output of the above code is

Input string: ABC789XYZ
Sum of all digits: 24

Using LINQ Approach

For a more concise solution, we can use LINQ to filter digits and calculate the sum

using System;
using System.Linq;

class Program {
   static void Main(string[] args) {
      string inputString = "Test123String456End";
      
      int sum = inputString
         .Where(char.IsDigit)
         .Sum(c => c - '0');
      
      Console.WriteLine("Input string: " + inputString);
      Console.WriteLine("Sum of digits: " + sum);
   }
}

The output of the above code is

Input string: Test123String456End
Sum of digits: 21

Comparison of Approaches

Conclusion

In this article, we explored multiple ways to find the sum of digits in a C# string. The char.IsDigit() method effectively identifies digit characters, while character arithmetic (c - '0') provides the fastest conversion from char to int. Choose the approach that best fits your needs based on readability and performance requirements.