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using System.Text;
public static class Raindrops
{
public static string Convert(int number)
{
var drops = new StringBuilder(15);
if (number % 3 == 0) drops.Append("Pling");
if (number % 5 == 0) drops.Append("Plang");
if (number % 7 == 0) drops.Append("Plong");
return drops.Length > 0 ? drops.ToString() : number.ToString();
}
}
We start by create a new StringBuilder instance:
var drops = new StringBuilder(15);
You may wonder why we're passing in 15 as the argument to the StringBuilder constructor?
Well, this sets the StringBuilder's internal capacity, which is the length of the internal char array it allocates to build the string in.
When a call would have the string exceed the internal capacity, a new and bigger char array is allocated.
We know beforehand that our returning string is never longer than 15 characters ("PlingPlangPlong"), so by explicitly specifying the capacity we prevent any unneeded allocations, which is good for memory and thus performance.
We can then use the remainder operator (%) in an if-statement to check if the number is a multiple of 3, and if so, append "Pling" to the StringBuilder:
if (number % 3 == 0) drops.Append("Pling");
We then do the same for the other two sounds:
if (number % 5 == 0) drops.Append("Plang");
if (number % 7 == 0) drops.Append("Plong");
Finally, we use the ternary operator to see if the StringBuilder is not empty (drops.Length > 0), and if so, we convert the StringBuilder to a string via its ToString() method. If it does have length zero, we convert the input number to its string representation:
return drops.Length > 0 ? drops.ToString() : number.ToString();
