I would like to know the Big O notation of the Char.IsLetter() function.

private bool Helper(char c)
{
    return char.IsLetter(c);
}

I believe that it has runtime complexity O(1). Is this correct? How can I verify this property for built-in functions?

CodePudding user response：

The runtime complexity of the char.IsLetter() method in C# is O(1). This means that the time it takes for the method to execute is constant and does not depend on the input size.

In the code you provided, the Helper() method simply calls the char.IsLetter() method and returns the result. Since the char.IsLetter() method has a runtime complexity of O(1), the Helper() method also has a runtime complexity of O(1).

It is worth mentioning that the runtime complexity of a method is not always a good indication of its performance. For example, a method with a runtime complexity of O(1) might still be slower than a method with a higher runtime complexity if the constant factor in the O(1) complexity is very large. In general, it is best to measure the performance of a method using actual experiments rather than relying solely on theoretical estimates.