This is a Sudoku solver that uses arc consistency and domain splitting. Also able to tell if a board has no or many solutions.

Download SudokuSolver

In Java, to start a class we use:

public class fileName
{

}

In a command line C++ program, the following lines are needed:

#include <iostream>
using namespace std;

iostream is needed for input and output, std is needed for basic functions like cout. Some online tutorials use #include <iostream.h> but apparently it’s deprecated.

The standard structure of a main method is:

int main () {

//Neat stuff goes here
return 0;

}

Printing

To print something, use  “cout” (console output?) with the insertion operator “<<” like this:

cout << “Hellos!\n”;

int a = 1;
int b = 2;
int c = a + b;
cout << “Some variable: ” << c << “\n” ; //Prints c
cout << “Some variable: ” << a+b << endl ; //Prints the same as above

The “\n” is needed to start a new line. This replaces System.out.println and System.out.print in Java. Alternatively, you can also use “endl” (end line).

The syntax for variable declarations are identical to Java with one small exception:

string a = “Feed me”; //OK
string a (“Feed me”); //OK, Identical to the line above.

Arrays

Java:

int[] myArray1 = new int[5];
int[][] myArray2 = new int[5][6];

C++:

int myArray1 [5];
int myArray2 [5][6];

Variables

Now this is pretty cool. When assigning a value to a variable, we can use a literal constant, an octal (base value, or a hex (base 16) value.

int a = 123; //Literal constant
a = 0173; //Octal (Start the variable with a 0)
a = 0×7b; //Hex (Start the variable with 0x)

Floating point numbers:

double a = 3.141592654
a = 6.02e23 //OK

Constants:

final int myVar = 100; //Java

const int myVar = 100; //C++

User Input

Use cin. Here is an example.

#include <iostream>
using namespace std;

int main () {
int i;
cout << “Enter a value…”;
cin >> i;
cout << “The value you entered is ” << i;
return 0;
}

Notice the use of the extraction operator “>>”. The line “cin >> i” takes the user input and stores it in the variable “i”. If the user enters a string instead of an integer, the program will not behave as you would expect. In Java, it will simply blow up. Also, the program will take whatever the user types up to a space, a tab, or a new line. Everything after these will be ignored unless you specifically store them in another variable. So, if a user enters a string which could possibly be composed of more than one word, it would be better to use the getline function.

The getline function works like this:

#include <iostream>
using namespace std;

int main () {
string i;
cout << “Enter a sentence…\n”;
getline (cin, i);
cout << “You said: ” << i;
return 0;
}

And its output may look something like this:

Enter a sentence…
C++ Rocks!
You said: C++ Rocks!

Control Structures

If, while, do while, and for statements are identical to Java.

Functions

Because C++ has a 1-pass compiler, any additional functions (a.k.a. “methods” in Java) must be declared before the main function.

For example, this will work:

#include <iostream>
using namespace std;

int addition (int a, int b)
{
int r;
r=a+b;
return (r);
}

int main ()
{
int z;
z = addition (5,3);
cout << “The result is “ << z;
return 0;
}

And this will not:

#include <iostream>
using namespace std;

int addition (int a, int b)
{
int r;
r=a+b;
return (r);
}

int main ()
{
int z;
z = addition (5,3);
cout << “The result is “ << z;
return 0;
}

Classes

A piece of sample code:

#include <iostream>
using namespace std;

class Point {
int x, y;
public:
Point (int, int);
void setPoint(int, int);
void printPoint() {
cout << “( ” << x << ” , ” << y << ” )” << endl;
}
};

Point::Point (int a, int b) {
x = a;
y = b;
}

void Point::setPoint(int a, int b) {
x = a;
y = b;
}

int main() {

Point foo(1,2);
foo.printPoint();
return 0;
}

This piece of code has an object with a constructor, two functions, and the main method creates one instance of the object.

Here is a quick Java application I whipped up. Quizzicle is a command line application that generates random math equations. You can choose an arithmetic operation, the number of questions, the number of digits in the question, and if negative numbers or zeros are allowed. Javadoc included.

Update 1.1:

• Adds a Timer
• Adds Logging (writing to a file)
• Various other minor features

I did not plan to release this one so you may see a few hacks.

Download Quizzicle 1.1

This guide will show beginner programmers how to set up and install JDK and the Eclipse IDE. I will be installing JDK 6 Update 7 and Eclipse 3.4.0 Ganymede.

Get JDK

Mac Users: Skip this as you already have JDK. Do a system update to check if you have latest one.

You will need to install JDK first by going to Java SE Downloads and choose “Java x Update y” where x is the latest version of Java and y is the latest non-beta update. (Do not get the version with NetBeans or Java EE unless you know what youre doing.) Installation is straightforward, but it may take some time. Go grab a coffee.

Get Eclipse

You can go to Eclipse.org’s Download Section and choose “Eclipse IDE for Java Developers.” Extract the contents of the zip file to wherever you wish.

Setting Up

Once you fire up Eclipse, it will ask you for a path to your workspace. This folder will contain all of the projects you create with Eclipse as subdirectories.

Once that’s done Eclipse will greet you with a Welcome window. Just click on “Go to Workbench” at the far right and you’ll never need to see this screen again.

Now we will make sure that Eclipse is using the Java SDK you just downloaded. Click Window > Preferences. Then, on the left panel expand Java, then click on Installed JREs. Make sure that the version of Java you installed is there and checked. If there are multiple items then, unless you plan to use them all, check only the version you downloaded.

If your version is not there, then click Add, choose Standard VM, and click next. Browse to X:\Program Files\Java\jreX.X.X_XX and everything should be filled out automatically. Click Finish.

Also make sure that the compliance level is set up properly. Click “Compiler” under “Java” and check the Compiler Compliance Level. If you are using JDK 6, then choose “1.6″ in the drop down menu. If you are using JDK 5 for some reason, then choose 1.5. Etc.

Testing Eclipse

Click File > New > Java Project and let’s make a simple HelloWorld project. Notice the workspace path and JRE that is being used. Then click Finish.

Create a class HelloWorld by clicking on the HelloWorld project folder on the left and clicking the “C+” icon in the toolbar. Name the new class HelloWorld and click Finish.

Paste the following code into HelloWorld.java.

public class HelloWorld
{
public static void main (String[] args)
{
System.out.println(“Hello Eclipse!”);
}
}

Then, click Run in the toolbar. The console at the bottom should say “Hello Eclipse!”

Additional Resources:

Dr. Java is a slimmer IDE that focuses on only the essentials. Try it if you need a more lightweight IDE. Also available for Mac OS X.

The Java SE 6 Documentation