CODEWITHSUNDEEP
c#
Georgi Delchev
Georgi Delchev

Reputation: 19

How to take digits from two different numbers and form a new one

I have the following problem here:My input is several lines of 2 digit numbers and I need to make a new number using the second digit of the first number and the first of the next one. Example:

int linesOfNumbers = Convert.ToInt32(Console.ReadLine());
for(int i = 0,i<linesOfNumbers,i++)
{
     int numbers = Conver.ToInt32(Console.ReadLine());
     //that's for reading the input
}

I know how to separate the numbers into digits.My question is how to merge them. For example if your input is 12 and 21 the output should be 22.

Upvotes: 1

Views: 697

Answers (6)

Sujit Singh
Sujit Singh

Reputation: 831

There are other solutions like substring, etc and many one have already given it above. I am giving the solution VIA LINQ, note that this isn't efficient and it's recommended only for learning purpose here 

 int numA = 12;
 int numB = 21 ;

 string secondPartofNumA = numA.ToString().Select(q => new string(q,1)).ToArray()[1]; // first digit
 string firstPartofNumB = numB.ToString().Select(q => new string(q,1)).ToArray()[0]; // second digit

 string resultAsString = secondPartofNumA + firstPartofNumB;
 int resultAsInt = Convert.ToInt32(resultAsString);

 Console.WriteLine(resultAsString);
 Console.WriteLine(resultAsInt);

Upvotes: -1

rweisse
rweisse

Reputation: 830

I hope this code snippet will help you combining your numbers. The modulo operator (%) means: 53 / 10 = 5 Rest 3

This example shows the computation of the numbers 34 and 12

int firstNumber = 34 - (34 % 10) // firstNumber = 30
int secondNumber = 12 % 10; // secondNumber = 2
int combined = firstNumber + secondNumber; // combined = 32

EDIT (added reading and ouput code):

boolean reading = true;
List<int> numbers = new ArrayList();
while(reading)
{
    try
    {
        int number = Convert.ToInt32(Console.ReadLine());
        if (number > 9 && number < 100) numbers.Add(number);
        else reading = false; // leave reading process if no 2-digit-number
    }
    catch (Exception ex)
    {
        // leave reading process by typing a character instead of a number;
        reading = false;
    }
}

if (numbers.Count() > 1)
{
    List<int> combined = new ArrayList();
    for (int i = 1; i <= numbers.Count(); i++)
    {
        combined.Add((numbers[i-1] % 10) + (numbers[i] - (numbers[i] % 10)));
    }

    //Logging output:
    foreach (int combination in combined) Console.WriteLine(combination);
}

Upvotes: 1

krillgar
krillgar

Reputation: 12815

I like oRole's answer, but I think they're missing a couple things with the example input that you provided in your comment. I'll also point out some of the errors in the code that you have.

First off, if you're only given the input 12,23,34,45, then you don't need to call Console.ReadLine within your for loop. You've already gotten the input, you don't need to get any more (from what you've described).

Secondly, unless you're doing mathematical operations, there is no need to store numerical data as ints, keep it as a string, especially in this case. (What I mean is that you don't store Zip Codes in a database as a number, you store it as a string.)

Now, onto the code. You had the right way to get your data:

var listOfNumbers = Console.ReadLine();

At that point, listOfNumbers is equal to "12,23,34,45". If you iterate on that variable as a string, you'll be taking each individual character, including the commas. To get each of the numbers to operate on, you'll need to use string.Split.

var numbers = listOfNumbers.Split(',');

This turns that list into four different two character numbers (in string form). Now, you can iterate over them, but you don't need to worry about converting them to numbers as you're operating on the characters in each string. Also, you'll need a results collection to put everything into.

var results = new List<string>();

// Instead of the regular "i < numbers.Length", we want to skip the last.
for (var i = 0; i < numbers.Length - 1; i++)
{
    var first = numbers[i];
    var second = numbers[i + 1]; // This is why we skip the last.

    results.Add(first[1] + second[0]);
}

Now your results is a collection of the numbers "22", "33", and "44". To get those back into a single string, you can use the helper method string.Join.

Console.WriteLine(string.Join(",", results));

Upvotes: 1

xland44
xland44

Reputation: 9

The % and / signs are your savior.

If you want the 'ones' digit of a number (lets call it X), simply do X%10 - the remainder will be whatever number is in the 'ones' digit. (23%10=3)

If, instead, the number is two digits and you want the 'tens' digit, divide it by ten. (19/10=1).

To merge them, multiply the number you want to be in the 'tens' digit by ten, and add the other number to it (2*10+2=22)

Upvotes: 0

oRole
oRole

Reputation: 1346

You could use the string-method .Substring(..) to achieve what you want.

If you want to keep int-conversion in combination with user input, you could do: 

int numA = 23;
int numB = 34;
int resultAB = Convert.ToInt16(numA.ToString().Substring(1, 1) + numB.ToString().Substring(0, 1));


Another option would be to take the users input as string values and to convert them afterwards like that:

string numC = "12";
string numD = "21";
int resultCD = Convert.ToInt16(numC.Substring(1, 1) + numD.Substring(0, 1));

Upvotes: 1

Nisarg Shah
Nisarg Shah

Reputation: 14561

As you mention, if you already have both numbers, and they are always valid two digit integers, following code should work for you.

var num1 = 12;
var num2 = 22;
var result = (num2 / 10)*10 + (num1 % 10);

num2/10 returns the first digit of second number, and num1 % 10 returns the second digit of the first number.

Upvotes: 0

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