Best logic for printing a specific pattern

Question

how to print the below pattern using only one loop?

*
**
***
****
*****




for(int i=1;i<=5;i++)
{
for(int j=1;j<=i;j++)
{
print("*");
}
print("\n");
}
every one know this, but using only on loop how?
it's really an interview question.he asked me that he will ask next question after answering this.