/* ============================================================================
 * File: Fibonacci2.java
 * ----------------------------------------------------------------------------
 *
 * This file is part of the Microsoft Supplemental UI Library for Visual J# .NET
 * Code Samples.
 *
 * Copyright (C)  2003  Microsoft Corporation. All rights reserved.
 *
 * THIS CODE AND INFORMATION ARE PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND,
 * WHETHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A PARTICULAR PURPOSE.
 * ============================================================================
 */

package RecursionDemo;

/**
 * This class implements RecursiveFunction interface to demonstrate calculation of
 * Fibonacci numbers as recursive funtion.  The code is optimized to recurse once only.
 * Refer Factorial.java also.
 */
public class Fibonacci2 implements RecursiveFunction {
    private RecursionStack stack;

    public String getName() {
        return "Fibonacci Function (optimized)";
    }
    
    public String getDescription() {
        return "This function generates Fibonacci numbers." +
            "  Fibonacci numbers are 0, 1, 1, 2, 3, 5, 8, 13, ..." +
            " i.e. the next number is sum of previous two numbers." +
            "  However instead of using double recursion it remembers one value" +
            " and uses only single recursion.";
    }

    public String getCode() {
        return "public int[] fibonacci2(int n) {\n" +
            "    if (n <= 1)\n" +
            "        return new int[] {0, 0};\n" +
            "    else if (n == 2)\n" +
            "        return new int[] {0, 1};\n" +
            "    else {\n" +
            "        int[] n1 = fibonacci2(n - 1);\n" +
            "        return new int[] {n1[1], n1[0] + n1[1]};\n" +
            "    }\n" +
            "}";
    }

    public int doRecursion(int n) {
        return (fibonacci2(n))[0];
    }

    public int[] fibonacci2(int n) {
        stack.push(n);

        int[] retVal;
        if (n <= 1)
            retVal = new int[] {0, 0};
        else if (n == 2)
            retVal = new int[] {0, 0};
        else {
            int[] n1 = fibonacci2(n - 1);
            retVal = new int[] {n1[1], n1[0] + n1[1]};
        }

        stack.pop(retVal[1]);

        return retVal;
    }

    public void setRecursionStack(RecursionStack s) {
        stack = s;
    }
}