public class Fibonacci4 {

    // Same counter as before.
    static int numCalls;

    // We'll use an array to record previously computed values:
    static int[] fValues;

    public static void main (String[] argv)
    {
        // Test case 1:
        int n = 5;
        // Initialize both the counter and the array:
        numCalls = 0;
        fValues = new int [n+1];
        int f = fibonacci (n);
        System.out.println ("f(" + n + ") = " + f + "    numCalls=" + numCalls);

        // Test case 2:
        n = 20;
        // Initialize both the counter and the array:
        numCalls = 0;
        fValues = new int [n+1];
        f = fibonacci (n);
        System.out.println ("f(" + n + ") = " + f + "    numCalls=" + numCalls);
    }


    static int fibonacci (int n)
    {
        // We are recording the number of times this method is called.
        numCalls ++;
        
        if (n <= 2) {
            // First time we reach here, we store the values.
            fValues[n] = n-1;
            return (n-1);
        }
        
        // If the values haven't been computed, then compute and store.
        if (fValues[n-1] == 0) {
            fValues[n-1] = fibonacci(n-1);
        }
        if (fValues[n-2] == 0) {
            fValues[n-2] = fibonacci(n-2);
        }

        // By the time we reach here, previous fib values have been stored.
        fValues[n] = fValues[n-1] + fValues[n-2];

        return fValues[n];
    }

}