Class 10-20 Notes CS 107
Wednesday, October 20, 2010 2:40 PM
Announcements: Sorry, but grades not yet ready to be posted. Maybe tonight? Remember that midterm #2 is next week, in lab, and in class next Friday Questions? Last Time: Mostly comments on program #4 Today: Other Approaches to Sorting Arrays examples: Searching, Command line args, Dynamic Array using ArrayList, Multidimensional array See other approaches to sorting given online on the course web site: http://people.cs.ubc.ca/~harrison/Java/sorting-demo.html
A funny thing happened to me the other day... 15 32768 14 16384 13 8192 12 4096 11 2048 10 1024 9 512 8 256 7 128 6 192 5 160 4 144 3 152 2 148 1 146 0 145
Binary Search
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Binary Search
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Arrays Examples: Command Line Args
/** * Show how we can retrieve command line arguments within the program */ import java.io.*; class CommandLineArgs { public static void main(String[] args) { System.out.println("Command line args are:"); int argsSize = args.length; for (int i=0; i<argsSize; i++) { System.out.println("[" + i + "]: " + args[i]); if (args[i].equals("tough")) { System.out.println("OK, starting the chess program in supertough mode..."); } }//end for } } Pasted from <http://logos.cs.uic.edu/Examples%20And% 20Notes/notes/Java/ArraysAverageGrades/CommandLineArgs/CommandLineArgs.java>
Run this from the command line to illustrate how command line args are passed into the program. To run this from within Eclipse, select File/Properties, then under Run/Debug settings create a new Launch Configuration, as a Java Application. Then select the "Arguments" tab and supply the args.
Arrays Examples: Dynamic Array What if the size of the array keeps changing while the program runs? a. Create our own;. See code online to this illustrate at: http://logos.cs.uic.edu/Examples%20And% 20Notes/notes/Java/ArraysAverageGrades/Arrays.htm b. Use the built-in ArrayList. Again see the above link for the code.
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Multidimensional Arrays: Example to do Character Recognition:
/** * Program to illustrate a 2-dimensional array used for character recognition. * * @author Dale Reed * @version 3/8/04 * Running program gives: Average y-value is: 5 */ public class CharRecognition { int[][] charArray = { {0,0,0,0,0,0,0,0,0,0,1,0,0,0,0}, {0,0,0,0,0,0,0,0,0,1,1,0,0,0,0}, {0,0,0,0,0,0,0,0,1,0,1,1,0,0,0}, {0,0,0,0,0,0,0,1,0,0,0,1,1,0,0}, {0,0,0,0,0,0,1,0,0,0,0,0,1,1,0}, {0,0,0,0,0,0,1,1,1,1,1,1,1,1,0}, {0,0,0,0,0,1,1,1,1,1,1,1,1,0,0}, {0,0,0,0,1,1,0,0,0,0,0,0,0,1,0}, {0,0,0,1,1,1,0,0,0,0,0,0,0,1,1}, {0,0,0,1,1,0,0,0,0,0,0,0,0,1,1}, {0,0,0,1,1,0,0,0,0,0,0,0,0,1,1}, {0,1,0,1,1,0,0,0,0,0,0,1,1,1,1}, {1,1,1,1,1,0,0,0,0,0,1,1,1,1,1}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0,0,0,0,0,0} }; public static void main(String[] args) { CharRecognition charRecognitionInstance = new CharRecognition(); charRecognitionInstance.doIt(); } public void doIt() { int result = this.averageYValue( charArray); System.out.println("Average y-value is: " + result + "\n"); } /** * Find the average y value in the 2-d array, which * represents a character. */ private int averageYValue( int array[][]) { int count= 0; /* Count how many are found */ int sum= 0; /* sum y position of those found */ int x, y; /* loop counters for x & y dimensions */
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for (x=0; x< array.length; x++)
{
for (y = 0; y < array[x].length; y++) { if ( array[x][y] == 1) { count++; sum+= y; break; /*leave the inner loop and check next row */ } /* end if */ } /* end for (y = ...*/ } /* end for (x = ... */ return sum/count; } }
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