Please help me to find out what is wrong

Question

My question is :
You are given a program that outputs all the numbers from 0 to 20.
Change the code to make it output only numbers that are multiples of 3.
Note :Be attentive and don't output 0.

My conte is :
#include <iostream>
using namespace std;

int main()
{

int num = 0;
while(num<=20){
num+=3;
if (num %3==0)
cout << num << endl;
}
return 0;
}

My output is :
3
6
9
12
15
18
21

But expected output :
3
6
9
12
15
18

How can I remove 21 from my code?

Edit : I found the answer.
https://code.sololearn.com/cmjqMRTEfp1H/?ref=app

Answer 1

just move the update statement (num += 3) after printing the result.
https://code.sololearn.com/cr08RlY26jsQ/?ref=app

Answer 2

You could also just change the condition to
while(num < 18)
and keep the rest the same.

Answer 3

You have to change int num = 0 to int num = 3 😊😊😊

Answer 4

If you want to respect the text of the problem...

"You are given a program that outputs all the numbers from 0 to 20.
Change the code to make it output only numbers that are multiples of 3.

Be attentive and don't output 0."

... this is the answer:

#include <iostream>
using namespace std;

int main()
{
//change the code
int num = 0;
while(num<=20){
if ((num != 0) && (num %3 == 0))
cout<<num<<endl;
num+=1;
}

return 0;
}

Answer 5

/*im using this, is it the right way?

i change this : while (num +1<=20) */

#include <iostream>
using namespace std;

int main()
{
//change the code
int num = 3;
while(num+1 <=20){
cout<<num<<endl;
num+=3;
}

return 0;
}

Answer 6

All of your answers do not meet the requirements of the problem: "outputs all the numbers from 0 to 20. Change the code..." 😉 Don't use "num+=3"... start from num=0... check if ((num != 0) && (num %3 == 0))