Problem with an int array

Elsydeon · #1 03-Sep-2005, 15:14

Well, the second lab is much easier... logically I get it all. I'm just running into a problem with an array I need to get working.

Basically it's a piece of the knight's tour. Not the entire program. I have to write a method that will check if the square the knight is jumping to is a valid move. Meaning it's not off the board, and the knight hasn't visited it before.

Seems very short and simple, and the main is just how I wanted to display it to him in class, not what will be the tour program at all. The only problem is in the method validMove itself. Here's what I've got.

CPP / C++ / C Code:

#include <iostream.h>
#include <iomanip.h>
#include <stdlib.h>


class knightTour {
	//Handles logic problem of Knight's tour
	//Maximum board size 20x20
public:
	bool validMove(int row, int col);


};//class knightTour

const maxSize=20;
typedef int boardType[maxSize][maxSize];

void main(){
	knightTour check;
	int row, col;
	cout<<"Enter the board location you wish to test:"<<endl;
	cout<<"Board row number: ";
	cin>>row;
	cout<<endl;
	cout<<"Board column number: ";
	cin>>col;
	cout<<endl;
	
	check.validMove(row, col);

}

bool knightTour::validMove(int row, int col){
	if(row>maxSize || col>maxSize || (row>maxSize && col>maxSize) || row<0 || col<0 || (row<0 && col<0)){
		return 1;
	}
//	else{
//		if((boardType[row][col]) == 0){
//			return 0;
//		}
//		else{
//			return 1;
//		}
//		}
}

I commented out where I'm getting my problems. Why am I not able to look at a specific array location and check it? I thought it might be that it's not sent to the method, but any attempts to do that resulted in more compiler errors, and I'm not sure it even needs it. You can remove the comments and see what errors I got from it... Hopefully someone can offer me some sort direction. I'd appreciate it.

L7Sqr · #2 03-Sep-2005, 15:48

Quote:

typedef int boardType[maxSize][maxSize];

Careful here.
You are saying that you want the string boardType[maxSize][maxSize] to be an alias for int.
For instance:

CPP / C++ / C Code:

typedef int Blah;

int main ()
{
   Blah x = 2;
   std::cout << x << '\n';
   return 0;
}

Prints:
2

remove the typedef and simply say int boardType[max][max];
Or bool boardType[max][max];

[edit]
To better illustrate:
Using the above example

CPP / C++ / C Code:

Blah x = 2;
int y = 7;

std::cout << "Type x " << typeid(x).name() << '\n';
std::cout << "Type y " << typeid(y).name() << '\n';

On my system the output is:
Type x i
Type y i

Output of name() is system dependant however, you should notice that they are the same type.

WaltP · #3 04-Sep-2005, 01:25

Yeah, what he said.

Also, your if is:

CPP / C++ / C Code:

if(row>maxSize || col>maxSize || (row>maxSize && col>maxSize) || row<0 || col<0 || (row<0 && col<0))

Now by looking at it again, isn't

CPP / C++ / C Code:

if(row>maxSize || col>maxSize || (row>maxSize && col>maxSize)

redundant? "If row or col is greater than maxsize" already takes into account row and col greater, therefore all you really need is

CPP / C++ / C Code:

if (row>maxSize || col>maxSize || row<0 || col<0)

But then again, to be perfectly accurate, you really need

CPP / C++ / C Code:

if (row >= maxSize || 
    col >= maxSize || 
    row <  0       || 
    col <  0)

which also includes another way to reformat the statement for readability. Note the >=

Elsydeon · #4 05-Sep-2005, 09:24

One last thing I'm weird on...

CPP / C++ / C Code:

#include <iostream.h>
#include <iomanip.h>
#include <stdlib.h>


class knightTour {
	//Handles logic problem of Knight's tour
	//Maximum board size 20x20
public:
	bool validMove(int row, int col);


};//class knightTour

const maxSize=20;
int boardType[maxSize][maxSize];

void main(){
	knightTour check;
	int row, col;
	
	boardType[0][0]=1;
	boardType[2][1]=2;
	boardType[4][2]=3;
	boardType[3][4]=4;
	boardType[2][6]=5;
	boardType[4][5]=6;
	boardType[6][6]=7;

	cout<<"For reference, board locations 0,0 2,1 4,2 3,4 2,6 4,5 and 6,6 have been marked as already visited by the knight.";
	cout<<"Enter the board location you wish to test:"<<endl;
	cout<<"Board row number: "<<endl;
	cin>>row;
	cout<<endl;
	cout<<"Board column number: ";
	cin>>col;
	cout<<endl;
	
	check.validMove(row, col);

}

bool knightTour::validMove(int row, int col){
	if(row>=maxSize || col>=maxSize ||  row<0 || col<0){
		return 1;
		cout<<"Space falls off board";
	}
	else{
		if((boardType[row][col]) == 0){
			return 0;
			cout<<"Valid location";
		}
		else{
			return 1;
			cout<<"Space already visited";
		}
		}
}

Having not messed with bool enough, or classes and methods in general, I don't know how to do my last little tweak. I want to get the couts outside of validMove and into main. Something like...

CPP / C++ / C Code:

if(check.validMove==1){
cout<<"Invalid move";
}

Now, obviously I know that doesn't work, I tried it. I just don't know how to do a test on the returned value from the method. Never done it before, and can't find it in the textbook I have.

cable_guy_67 · #5 05-Sep-2005, 10:29

Quote:

Originally Posted by Elsydeon

One last thing I'm weird on...

CPP / C++ / C Code:

if(check.validMove==1){
cout<<"Invalid move";
}

Now, obviously I know that doesn't work, I tried it. I just don't know how to do a test on the returned value from the method. Never done it before, and can't find it in the textbook I have.

Maybe something like,

CPP / C++ / C Code:

if(check.validMove(int, int) == 1)

would be more appropriate.

Mark

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