package algs11;

import stdlib.StdDraw;
import stdlib.StdOut;
import stdlib.StdRandom;
import stdlib.Trace;

import java.util.Arrays;

/**
 * This is a skeleton file for your homework. Edit the sections marked TODO. You
 * may add new functions. You may also edit the function "main" to test your
 * code.
 *
 * You must not add static variables. You MAY add static functions, just not
 * static variables.
 *
 * It is okay to add functions, such as
 *
 * <pre>
 *     public static double sumHelper (double[] list, int i, double sumSoFar) {
 * </pre>
 *
 * but it is NOT okay to add static variables, such as
 *
 * <pre>
 * public static int x;
 * </pre>
 *
 * As for homework 1, you must not change the declaration of any method.
 * 
 * You can edit the main function all you want. I will not run your main
 * function when grading.
 */
public class MyRecursion {

        /**
         * As a model, here is a minValue function, both iteratively and recursively
         */
        /** iterative version */
        public static double minValueI (double[] list) {
                double result = list[0];
                int i = 1;
                while (i < list.length) {
                        if (list[i] < result) result = list[i];
                        i = i + 1;
                }
                return result;
        }

        /** recursive version */
        public static double minValue (double[] list) {
                return minValueHelper (list, 1, list[0]);
        }
        private static double minValueHelper (double[] list, int i, double result) {
                if (i < list.length) {
                        if (list[i] < result) result = list[i];
                        result = minValueHelper (list, i + 1, result);
                }
                return result;
        }

        /**
         * PROBLEM 1: Translate the following sum function from iterative to
         * recursive.
         *
         * You should write a helper method. You may not use any "fields" to solve
         * this problem (a field is a variable that is declared "outside" of the
         * function declaration --- either before or after).
         */
        public static double sumI (double[] a) {
                double result = 0.0;
                int i = 0;
                while (i < a.length) {
                        result = result + a[i];
                        i = i + 1;
                }
                return result;
        }
        public static double sum (double[] a) {
                // TODO
                return StdRandom.uniform ();
        }

        /**
         * PROBLEM 2: Do the same translation for this in-place reverse function
         *
         * You should write a helper method. You may not use any "fields" to solve
         * this problem (a field is a variable that is declared "outside" of the
         * function declaration --- either before or after).
         */
        public static void reverseI (double[] a) {
                int hi = a.length - 1;
                int lo = 0;
                while (lo < hi) {
                        double loVal = a[lo];
                        double hiVal = a[hi];
                        a[hi] = loVal;
                        a[lo] = hiVal;
                        lo = lo + 1;
                        hi = hi - 1;
                }
        }
        public static void reverse (double[] a) {
                // TODO
        }

        /**
         * PROBLEM 3: The following function draws mickey mouse, if you call it like
         * this from main:
         *
         * <pre>
         * draw (.5, .5, .25);
         * </pre>
         *
         * Change the code to draw mickey moose instead. Your solution should be
         * recursive.
         * 
         * Before picture:
         * http://reed.cs.depaul.edu/efredericks/ds1/images/MickeyMouse.png After picture:
         * http://reed.cs.depaul.edu/efredericks/ds1/images/MickeyMoose.png
         *
         * You may not use any "fields" to solve this problem (a field is a variable
         * that is declared "outside" of the function declaration --- either before
         * or after).
         */
        public static void draw (double centerX, double centerY, double radius) {
                // TODO 
                if (radius < .0005) return;

                StdDraw.setPenColor (StdDraw.LIGHT_GRAY);
                StdDraw.filledCircle (centerX, centerY, radius);
                StdDraw.setPenColor (StdDraw.BLACK);
                StdDraw.circle (centerX, centerY, radius);

                double change = radius * 0.90;

                StdDraw.setPenColor (StdDraw.LIGHT_GRAY);
                StdDraw.filledCircle (centerX + change, centerY + change, radius / 2);
                StdDraw.setPenColor (StdDraw.BLACK);
                StdDraw.circle (centerX + change, centerY + change, radius / 2);

                StdDraw.setPenColor (StdDraw.LIGHT_GRAY);
                StdDraw.filledCircle (centerX - change, centerY + change, radius / 2);
                StdDraw.setPenColor (StdDraw.BLACK);
                StdDraw.circle (centerX - change, centerY + change, radius / 2);
        }

        /**
         * PROBLEM 4: Run runTerribleLoop for one hour. You can stop the program
         * using the red "stop" square in eclipse. Fill in the OUTPUT line below
         * with the numbers you saw LAST --- edit the line, replacing the two ...
         * with what you saw:
         *
         * OUTPUT: terribleFibonacci(...)=... // TODO
         *
         * Comment: the code uses "long" variables, which are like "int", but
         * bigger. It's because fibonacci numbers get really big really fast.
         */
        public static void runTerribleLoop () {
                for (int N = 0; N < 100; N++)
                        StdOut.format ("terribleFibonacci(%2d)=%d\n", N, terribleFibonacci (N));
        }
        public static long terribleFibonacci (int n) {
                if (n <= 1) return n;
                return terribleFibonacci (n - 1) + terribleFibonacci (n - 2);
        }

        /**
         * PROBLEM 5: The implementation of terribleFibonacci is TERRIBLE! Write a
         * more efficient version of fibonacci. Do not change runFibonacciLoop or
         * runFibonacciSomeValues.
         *
         * To make fibonacci run faster, you want it so that each call to
         * fibonacci(n) computes the fibonacci numbers between 0 and n once, not
         * over and over again.
         *
         * Comment: You will want to use a local variable of type "long" rather than
         * type "int", for the reasons discussed above.
         *
         * Comment: At some point, your fibonacci numbers might become negative.
         * This is normal and expected.
         * http://en.wikipedia.org/wiki/Integer_overflow We discuss this at length
         * in our systems classes.
         *
         * You may not use any "fields" to solve this problem (a field is a variable
         * that is declared "outside" of the function declaration --- either before
         * or after).
         * 
         * You may use a loop on this problem.
         * You do not need to use recursion.
         */
        public static void runFibonacciLoop () {
                for (int N = 0; N < 100; N++)
                        StdOut.format ("fibonacci(%2d)=%d\n", N, fibonacci (N));
        }
        public static long fibonacci (int n) {
                return 0; // TODO
        }

        /**
         * A test program, using private helper functions.  See below.
         * To make typing tests a little easier, I've written a function to convert strings to arrays.  See below.
         * You can modify this -- it is not graded.
         */
        public static void main (String[] args) {
                testSum ("11 21 81 -41 51 61");
                testSum ("11 21 81 -41 51");
                testSum ("11 21 81 -41");
                testSum ("11 21 81");
                testSum ("11 21");
                testSum ("11");
                testSum ("");

                testReverse ("11 21 81 -41 51 61");
                testReverse ("11 21 81 -41 51");
                testReverse ("11 21 81 -41");
                testReverse ("11 21 81");
                testReverse ("11 21");
                testReverse ("11");
                testReverse ("");

                testFibonacci (0, 0);
                testFibonacci (1, 1);
                testFibonacci (1, 2);
                testFibonacci (2, 3);
                testFibonacci (21, 8);
                testFibonacci (233, 13);
                testFibonacci (75025, 25);
                testFibonacci (             1_836_311_903L, 46);
                testFibonacci (             2_971_215_073L, 47);
                testFibonacci (       308_061_521_170_129L, 71); 
                testFibonacci (       498_454_011_879_264L, 72);
                testFibonacci ( 7_540_113_804_746_346_429L, 92);
                testFibonacci (-6_246_583_658_587_674_878L, 93);
                testFibonacci (  -813_251_414_217_914_645L, 376);
                StdOut.println ("Finished tests");

                draw (.5, .5, .25);

                // TODO: uncomment these temporarily when you want to see the output of your Fibonacci functions
                //runTerribleLoop ();   
                //runFibonacciLoop();           
        }
        
        /*
         * A main function for debugging -- change the name to "main" to run it (and
         * rename the existing main method to something else). Change the test as
         * appropriate.
         */
        public static void main1 (String[] args) {
                Trace.drawStepsOfMethod ("minValueI");
                Trace.drawStepsOfMethod ("minValue");
                Trace.drawStepsOfMethod ("minValueHelper");
                Trace.run ();
                testMinValue ("11 21 9 31 41");
        }

        /* Test functions --- lot's of similar code! */
        private static void testSum (String list) {
                double[] aList = doublesFromString (list);
                double expected = sumI (aList);
                double actual = sum (aList);
                if (! Arrays.equals (aList, doublesFromString (list))) {
                        StdOut.format ("Failed sum([%s]): Array modified\n", list);
                }
                if (expected != actual) {
                        StdOut.format ("Failed sum([%s]): Expecting (%.1f) Actual (%.1f)\n", list, expected, actual);
                }
        }
        private static void testMinValue (String list) {
                double[] aList = doublesFromString (list);
                double expected = minValueI (aList);
                double actual = minValue (aList);
                if (! Arrays.equals (aList, doublesFromString (list))) {
                        StdOut.format ("Failed minValue([%s]): Array modified\n", list);
                }
                if (expected != actual) {
                        StdOut.format ("Failed minValue([%s]): Expecting (%.1f) Actual (%.1f)\n", list, expected, actual);
                }
        }
        private static void testReverse (String list) {
                double[] expected = doublesFromString (list);
                reverseI (expected);
                double[] actual = doublesFromString (list);
                reverse (actual);
                // != does not do what we want on arrays
                if (! Arrays.equals (expected, actual)) {
                        StdOut.format ("Failed reverse([%s]): Expecting (%s) Actual (%s)\n", list, Arrays.toString (expected), Arrays.toString (actual));
                }
        }
        private static void testFibonacci (long expected, int n) {
                long actual = fibonacci (n);
                if (expected != actual) {
                        StdOut.format ("Failed fibonacci(%d): Expecting (%d) Actual (%d)\n", n, expected, actual);
                }
        }

        /* A utility function to create an array of doubles from a string. */
        // The string should include a list of numbers, separated by single spaces.
        private static double[] doublesFromString (String s) {
                if ("".equals (s)) return new double [0]; // empty array is a special case
                String[] nums = s.split (" ");
                double[] result = new double[nums.length];
                for (int i = nums.length-1; i >= 0; i--) {
                        try { 
                                result[i] = Double.parseDouble (nums[i]); 
                        } catch (NumberFormatException e) { 
                                throw new IllegalArgumentException (String.format ("Bad argument \"%s\": could not parse \"%s\" as a double", s, nums[i]));
                        }
                }
                return result;
        }
}