Programming Forums > Application Development > C++

quantalfred · Jan 30th, 2005, 11:39 PM

Hi all,

I'm a beginner of C++. I'd like to ask how I could input an integer n, and after running the program, return an array with length n.

kurifu · Jan 31st, 2005, 3:42 AM

(Toggle Plain Text)

void main( )
{
  int n = 0;
  cin >> n;

  char *ptr = new char( n );
  return ptr; // WTF?
}

Just for the record, that will not return the array though... applications only return numeric values... not arrays. Perhaps you mean have a function which returns the array? Well that demonstrates how to do it, just remember to release you pointer when you are done with it.

quantalfred · Jan 31st, 2005, 8:14 AM

In fact I just want to input an integer n and then I can form an array with length n which can be used in the main program.

Ooble · Jan 31st, 2005, 5:49 PM

You can't define an array with a variable length. You can, however, use memory allocation to do the same thing:

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int i;
 cin >> i;
 int *array = new int[i];

At the end of the program, you then have to free the memory. Use:

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delete [] array;

You should really know how to work pointers before you mess with this though.

Xero · Jan 31st, 2005, 5:50 PM

Quote:

Originally Posted by Ooble

You can't define an array with a variable length. You can, however, use memory allocation to do the same thing:

(Toggle Plain Text)

int i;
cin >> i;
int array = new int[i];

(I think that's right.)

u missed the pointer derefference *

haha beat u by 10 seconds or so

Ooble · Jan 31st, 2005, 5:55 PM

Heh. Forgot about it until I'd posted.

Mjordan2nd · Jan 31st, 2005, 6:10 PM

Heh. Guess you guys are correct. I've been getting too used to Java.

quantalfred · Jan 31st, 2005, 11:14 PM

Thanks all for replying. But if I want to creat a two-dimensional array, how could I modify the code?

(Toggle Plain Text)

cin >> n;
double *array = new array[n][n];

delete array;

It seems that it doesn't work...

Xero · Feb 1st, 2005, 1:27 AM

Quote:

Originally Posted by quantalfred

Thanks all for replying. But if I want to creat a two-dimensional array, how could I modify the code?

(Toggle Plain Text)

cin >> n;
double *array = new array[n][n];

delete array;

It seems that it doesn't work...

#1 its new "double", not new "array"
#2 u need a double pointer, I believe ** (not so sure about this but i think thats what u need. I havent used them that often.)
#3 your delete needs brackets [][]. Delete alone is used for a single variable. Arrays are different.

(Toggle Plain Text)

cin >> n;
double **array = new double[n][n];

delete array[][];

quantalfred · Feb 1st, 2005, 8:03 AM

Quote:

Originally Posted by Xero

#1 its new "double", not new "array"
#2 u need a double pointer, I believe ** (not so sure about this but i think thats what u need. I havent used them that often.)
#3 your delete needs brackets [][]. Delete alone is used for a single variable. Arrays are different.

(Toggle Plain Text)

cin >> n;
double **array = new double[n][n];

delete array[][];

It said, error C2440: 'initializing' : cannot convert from 'double (*)[1]' to 'double ** ', after compiling. I can't find the right way to write a double pointer...

Jan 31st, 2005, 5:49 PM	#4
Ooble I eat cake for breakfast. Join Date: Jul 2004 Location: In my box. Posts: 4,434 Rep Power: 9	You can't define an array with a variable length. You can, however, use memory allocation to do the same thing: (Toggle Plain Text) int i; cin >> i; int array = new int[i]; int i; cin >> i; int array = new int[i]; At the end of the program, you then have to free the memory. Use: (Toggle Plain Text) delete [] array; delete [] array; You should really know how to work pointers before you mess with this though. __________________ Me :: You :: Them

Jan 31st, 2005, 5:55 PM	#6
Ooble I eat cake for breakfast. Join Date: Jul 2004 Location: In my box. Posts: 4,434 Rep Power: 9	Heh. Forgot about it until I'd posted. __________________ Me :: You :: Them

Jan 31st, 2005, 6:10 PM	#7
Mjordan2nd The Supreme Ruler Join Date: May 2004 Location: Houston Posts: 1,476 Rep Power: 6	Heh. Guess you guys are correct. I've been getting too used to Java. __________________ "Every gun that is made, every warship launched, every rocket signifies, in the final sense, a theft from those who hunger and are not fed, from those who are cold and are not clothed. The world in arms is not spending money alone. It is spending the sweat of its laborers, the genius of its scientists, the hopes of its children." - Dwight D. Eisenhower

Jan 31st, 2005, 11:14 PM	#8
quantalfred Newbie Join Date: Jan 2005 Posts: 21 Rep Power: 0	follow up question Thanks all for replying. But if I want to creat a two-dimensional array, how could I modify the code? (Toggle Plain Text) cin >> n; double array = new array[n][n]; delete array; cin >> n; double array = new array[n][n]; delete array; It seems that it doesn't work...

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Jan 30th, 2005, 11:39 PM	#1
quantalfred Newbie Join Date: Jan 2005 Posts: 21 Rep Power: 0	A problem Hi all, I'm a beginner of C++. I'd like to ask how I could input an integer n, and after running the program, return an array with length n.

Jan 31st, 2005, 3:42 AM	#2
kurifu Expert Programmer Join Date: Jul 2004 Location: Halifax, Nova Scotia (Canada) Posts: 784 Rep Power: 5	(Toggle Plain Text) void main( ) { int n = 0; cin >> n; char ptr = new char( n ); return ptr; // WTF? } void main( ) { int n = 0; cin >> n; char ptr = new char( n ); return ptr; // WTF? } Just for the record, that will not return the array though... applications only return numeric values... not arrays. Perhaps you mean have a function which returns the array? Well that demonstrates how to do it, just remember to release you pointer when you are done with it. __________________ Clifford Matthew Roche <geek@cliffordroche.com> Web Hosting: http://www.crd-hosting.com Consulting: http://www.crdev-consulting.com

Jan 31st, 2005, 8:14 AM	#3
quantalfred Newbie Join Date: Jan 2005 Posts: 21 Rep Power: 0	In fact I just want to input an integer n and then I can form an array with length n which can be used in the main program.

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Programming Forums > Application Development > C++

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