How to print number sequence in reverse order?

Question

1.00/5 (2 votes)

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hi.. i want to print 5 digit number in reverse order..

ex.. 49999,49998,49997,49996.....so on

one more think number of print depend on user input
i.e if user input 3 then it display only 3 print as 49999,49998,49997

any idea?....thanks in advance...

What I have tried:

C#

for(int i =50000; i >=printCopies; i--)
{
   reslt += i.ToString("00000") + System.Environment.NewLine;
}

Posted 14-Jul-20 9:58am

Sam_gaik

Updated 14-Jul-20 23:12pm

v2

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Comments

Patrice T 14-Jul-20 16:41pm

What is the problem with your code?

Sam_gaik 14-Jul-20 17:01pm

It does not work as expected..

Patrice T 14-Jul-20 17:12pm

Elaborate.

3 solutions

Solution 3

Am I missing something here? Do you just want to print a line of comma separated decreasing values like this:

C#

 int copies = 3;
 int initialValue = 5000;
 string separator = string.Empty;
 for (int i=0;i <copies;i++)
 {
     Console.Write(separator);
     Console.Write(initialValue - i);
     if (separator.Length==0) separator = ",";
 }
Console.WriteLine();

If you want an IEnumerable so that you can use Linq to select the output. Try this

C#

  IEnumerable <int > numbers = Enumerable.Range(initialValue-copies+1, copies).Reverse();
  IEnumerable <string > numberStrings = Enumerable.Range(initialValue , copies).Select((x,i) = > (x-(i*2)).ToString());
 //print  one number per line
           foreach (int num in numbers)
            {
                Console.WriteLine(num);
            }
//use IEnumerable <string > to join the strings together to give a comma separated string value
            Console.WriteLine(string.Join(',', numberStrings));

Posted 14-Jul-20 23:12pm

George Swan

Comments

Sam_gaik 15-Jul-20 12:00pm

Thanks for your suggestion... !

Solution 2

That looks to be on the right track.

My only question/recommendation from what you have shown is in regards to reslt :
It should NOT be a String variable, because it is immutable. If this is the case; you should be replacing it with a StringBuilder, which is designed for this.

C#

StringBuilder sbResult = new StringBuilder();

for(int i =50000; i >=printCopies; i--)
{
	sbResult.AppendLine( i.ToString("00000") );
}

reslt = sbResult.ToString();

References:
MS Docs: Strings - C# Programming Guide[^]
MS Docs: StringBuilder Class (System.Text)[^]

Posted 14-Jul-20 10:15am

MadMyche

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OriginalGriff · Accepted Answer · 2020-07-14T10:10:00

Solution 1

Easiest way to understand is like this:

C#

StringBuilder sb = new StringBuilder();
for (int i = 0; i < userInputLimit; i++)
   {
   sb.AppendLine((50000 - i).ToString());
   }
string result = sb.ToString();

Using a StringBuilder is better than concatenating strings as it "expands" automatically instead of creating a new string every time you add a new bit to the old one.

Posted 14-Jul-20 10:10am

OriginalGriff

Comments

Sam_gaik 15-Jul-20 1:53am

It works...thnks

OriginalGriff 15-Jul-20 2:04am

You're welcome!