Can you explain what is meant by a method with caching results?

A method with caching results capability is a function that computes the result on the first call and saves it, so that subsequent calls with the same parameters return the stored value without recomputing. This improves performance, especially if computations are expensive in terms of time or resources.

In C#, this can be implemented, for example, using a dictionary to store results:

private Dictionary<int, int> cache = new Dictionary<int, int>();

public int ComputeFactorial(int n)
{
    if (cache.ContainsKey(n))
        return cache[n];

    int result = (n <= 1) ? 1 : n * ComputeFactorial(n - 1);
    cache[n] = result;
    return result;
}

Here, on subsequent calls with the same argument, the result is taken from cache, saving time.