Welcome! In today's lesson, we will explore the practical application of string operations and type conversions in C#. These concepts are essential and are utilized in various programming scenarios. We'll look at a real-world example: time parsing. Have you ever wondered how to add a specific number of seconds to a given time? By the end of today's session, you'll be equipped to calculate this using C#. Let's start!

Imagine this: You receive a time formatted as a string in HH:MM:SS, where HH, MM, and SS represent the hour, minute, and second, respectively. Additionally, you are given an integer representing a number of seconds. Your task is to compute the new time after adding the provided seconds and output the result in the HH:MM:SS format.

For example, if the input time is 05:10:30 and the number of seconds to add is 123, the output should be 05:12:33, since 123 seconds convert to 2 minutes and 3 seconds.

Take note of these points when resolving this task:

• The input time is a valid time string in the HH:MM:SS format, with HH ranging from 00 to 23, MM, and SS ranging from 00 to 59.
• The output should be in the same format.

Let's go ahead and break down how to accomplish this in our step-by-step solution guide.

Our initial step involves parsing the input time string. From this string, we'll extract the hours, minutes, and seconds as integer values for further calculations. In C#, we can utilize the Split() method along with int.Parse() or Convert.ToInt32() to divide the string at ":" and convert each substring into an integer:

C#
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1string time = "12:34:56";
2string[] timeParts = time.Split(':');
3int hours = int.Parse(timeParts[0]);
4int minutes = int.Parse(timeParts[1]);
5int seconds = int.Parse(timeParts[2]);

By executing this operation, we've successfully parsed the time string and converted the hours, minutes, and seconds into integers.

Now that we have the hours, minutes, and seconds as integers, we can easily calculate the total number of seconds elapsed since the start of the day. Here's the logic behind it:

• 1 hour comprises 3,600 seconds, so we multiply the number of hours by 3,600.
• 1 minute comprises 60 seconds, so we multiply the number of minutes by 60.
• The count of seconds remains unchanged.

In C#, we can write the following code:

C#
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1int secondsSinceStart = hours * 3600 + minutes * 60 + seconds;

Your function should now compute the cumulative number of seconds from the start of the day.

Next, we need to add the integer representing a number of seconds to our computed secondsSinceStart, and also handle situations where the additional seconds cause a day to roll over:

C#
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1int totalSeconds = (secondsSinceStart + seconds) % (24 * 3600);

The modulus operator (%) ensures that our totalSeconds value doesn't exceed the total number of seconds in a day (86,400 seconds or 24 * 3,600 seconds).

In this step, we reverse the previous operation. We're given an integer representing the number of seconds, and we need to convert this into a time string in the HH:MM:SS format.

We'll use integer division and the modulus operator to determine the hours, minutes, and seconds:

C#
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1int newHours = totalSeconds / 3600;
2int remainder = totalSeconds % 3600;
3int newMinutes = remainder / 60;
4int newSeconds = remainder % 60;

The final step is to assemble these values into an HH:MM:SS format string:

C#
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1return string.Format("{0:D2}:{1:D2}:{2:D2}", newHours, newMinutes, newSeconds);

This method ensures that each time value is a 2-digit number, padding with a zero if needed.

Let's integrate all the individual steps and present the final method:

C#
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1using System;
2
3public class Program
4{
5    public static void Main()
6    {
7        string inputTime = "05:10:30";
8        int secondsToAdd = 123;
9        
10        string newTime = CalculateNewTime(inputTime, secondsToAdd);
11        Console.WriteLine("New Time: " + newTime); // Expected Output: New Time: 05:12:33
12    }
13    
14    public static string CalculateNewTime(string time, int secondsToAdd)
15    {
16        string[] timeParts = time.Split(':');
17        int hours = int.Parse(timeParts[0]);
18        int minutes = int.Parse(timeParts[1]);
19        int seconds = int.Parse(timeParts[2]);
20        
21        int secondsSinceStart = hours * 3600 + minutes * 60 + seconds;
22        int totalSeconds = (secondsSinceStart + secondsToAdd) % (24 * 3600);
23        
24        int newHours = totalSeconds / 3600;
25        int remainder = totalSeconds % 3600;
26        int newMinutes = remainder / 60;
27        int newSeconds = remainder % 60;
28        
29        return string.Format("{0:D2}:{1:D2}:{2:D2}", newHours, newMinutes, newSeconds);
30    }
31}

And voila! You've crafted a method that accurately calculates the new time based on the provided time and the number of seconds elapsed since then.

Congratulations! You've adeptly learned how to parse a time string and employ type conversions to calculate the number of seconds that have passed since the day's start. You also learned how to perform the reverse operation: calculate the time based on the number of seconds passed since the beginning of the day. In this lesson, we've practiced essential C# skills, including string operations, converting strings to integers, and formatting output. Continue practicing with similar problems to reinforce your learning, and you'll soon find these tasks becoming second nature. In our upcoming sessions, more practical exercises related to this topic await. See you there, and happy coding!