数的负指数

Question

I made this program to find the power of any number using recursion and it works, but also I need to find negative power of the number, for example, I have the base = 2 and the exponent = -3 so the result = 0.125, what should I do?

public static int power(int x, int n )
        {
            if (n < 0)
            {
                Console.WriteLine("invalid");
                return 0;
            }
            else if (n == 1)
            {
                return x;
            }
            else if (n == 0)
            {
                return 1;
            }
            else
            {
                return x * power(x, n - 1);
            }
        }

        static void Main(string[] args)
        {
            Console.Write("enter the base: ");
            int x = int.Parse(Console.ReadLine());
            Console.Write("enter the power:");
            int n = int.Parse(Console.ReadLine());
            int z = power(x, n);
            Console.WriteLine(z);
        }

Answer 1

Since the result of raising a number to a negative power is just 1 divided by the number raised to the non-negative power, you can change you method like so (note that we also need to return a double type, since we're dealing with fractional values):

public static double power(int x, int n)
{
    if (n < 0) return 1 / power(x, -n);  // recursive call with '-n' for negative powers
    if (n == 0) return 1;
    if (n == 1) return x;
    return x * power(x, n - 1);
}

Now it works with negative numbers:

public static void Main(string[] args)
{
    Console.WriteLine(power(2, -3));
    GetKeyFromUser("\nDone! Press any key to exit...");
}

Output