001package algs11;
002
003import stdlib.StdOut;
004
005// Homework 2, Parts 2 and 3 (Version 2)
006//
007// Part 1. See MyDebugging.java.
008//
009// Part 2.
010// The motivation for this homework is to help you develop the mental model for how Java
011// functions and loops execute.
012//
013// TODO: Hand-trace the examples given in the main program. There are three of them.
014// You only need to trace the execution of the max method, from the beginning to the end.
015// Be sure to show how each variable changes. You do not need to show line numbers
016// in your traces.
017//
018// Scan your traces and submit them. Or you can do it in ASCII or a Word document.
019//
020// Part 3.
021// Re-write the max function on paper, or in a Word document, using a for loop.
022//
023// TODO: Hand in your new max method with a for loop.
024//
025// Both your traces and your new max method should be in the same file as Part 1.
026// Upload a scan of your handwritten answers or your Word document to D2L.
027//
028// DO NOT TAKE A PICTURE WITH YOUR PHONE.
029//
030// You do not need to hand in this file!
031//
032
033public class MyMaxTrace {
034    public static Double max(double[] a) {
035        if (a.length == 0) {
036            throw new IllegalArgumentException();
037        }
038
039        // DO NOT change this to "double" with a lower-case "d."
040        Double m = a[0];
041        int i = 1;
042        while (i < a.length) {
043            if (m < a[i]) {
044                m = a[i];
045            }
046            i += 1;
047        }
048        return m;
049    }
050
051    public static void testMax(double expected, double[] a) {
052        Double actual = max(a);
053        if (expected != actual) {
054            StdOut.format("max failed: Expecting [%d] Actual [%d] with argument %s\n", expected, actual, java.util.Arrays.toString(a));
055        }
056    }
057
058    public static void main(String[] args) {
059        // Test 1
060        testMax(31, new double[]{11, 21, 31});
061
062        // Test 2
063        testMax(31, new double[]{31, 11, 21});
064
065        // Test 3
066        testMax(81, new double[]{21, 31, 11, 71, 51, 81, 41});
067    }
068}