How do I remove comma after last number/output loop in C++

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when i input
a = 1
b = 20

my output is always :
"3 , 9 , 15 , ."

but what i wanted is :
"3 , 9 , 15."

PS : SOrry for my bad english, i hope you guys understand
i just need an example or solution to this program

What I have tried:

int a,b;

cout<< "Number 1 = ";
cin>>a;
cout<< "Number 2 = ";
cin>>b;

if(a<=b)
{
    for(a;a<=b;a++)
    {
        if(a%3==0&&a%2!=0)
        {
            cout<<a;
        }
        if(a<b&&a%3==0&&a%2!=0)
        {
            cout<< " , ";
        }
        else if(a==b)
        {
            cout<< ".";
        }

Posted 3-Nov-17 8:47am

Member 13502043

Updated 3-Nov-17 20:51pm

v3

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enhzflep 5-Nov-17 2:06am

While i see you've already reached a solution, there is another way to think about the problem.
No one I've met actually puts commas _after_ numbers when writing them in a list. What they do is put commas _before_ numbers that aren't the first in a list.

So, if you consider a for loop that prints out the value of the loop counter, the way you do it is to print a comma before the number, provided the loop counter doesnt hold its initial value. Once all the numbers have been printed, spit-out a full-stop and you're done.

My code improved once i looked at the problem from this different perspective. :)

3 solutions

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Rick York · Answer 1 · 2017-11-03T10:04:00

Solution 1

You could write the if-else logic like this :

C++

if( ( a % 3 == 0 ) && ( a % 2 != 0 ) )
{
    cout << a;
    if( a == b )
        cout << ".";
    else
        cout << " , ";
}

Posted 3-Nov-17 10:04am

Rick York

v2

Patrice T · Answer 2 · 2017-11-03T14:14:00

First, a little analyze:
The '.' will be always printed and always be last. Which means simplification

C++

if(a<=b)
{
    for(a;a<=b;a++)
    {
        if(a%3==0&&a%2!=0)
        {
            cout<<a;
            if(a<b)
            {
                cout<< " , ";
            }
        }
    }
    cout<< ".";
}

The problem in your code is that b will not necessary be printed.
There is many solution around this
- if you print the comma after a number, you need to make sure there will be a next number to print.
- if toy print the comma before a number, you need to make sure it is not the first.

Member 13502043 · Answer 3 · 2017-11-03T20:29:00

Solution 3

Thanks guys but i already got my solution to put

char const*sep = ""

....
for(a;a<=b;a++)
    	{
		if(a%3 == 0 && a%2 != 0)
    		{		   
       		        cout << sep << a; 
       			sep = ", ";
    		}
    	}

Posted 3-Nov-17 20:29pm