RE: [Dev-C++] q3??

[Ioannis V. <no...@ho...>]

>From: senem beken <sbe...@ya...>
>To: dev...@li...
>Subject: [Dev-C++] q3??
>Date: Thu, 5 Sep 2002 02:49:38 -0700 (PDT)

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


Or better: #include <cstdlib>



>int main()
>{
>       int nrows,ncolumns;
>       nrows=ncolumns=5;
>        int **arr=new int*[nrows];
>        for(int i=0;i<ncolumns;i++) //why do i have to use a for loop
>          arr[i]=new int[ncolumns];  //to create a multiple subs array
>                                     // dynamically??
>                                    //why can't i use  a code like:
>                                    //int **arr=new int*[nrows];
>                                    // *arr=new int[ncolumns];   ???




You can:

#include <iostream>
#include <vector>

int main() try
{
 using std::vector;

 int (*p)[50];

// Creates an 100x50 array on the free store
 p=new int[100][50];

 delete[] p;


 // A second way:

 typedef int array[50];

// Creates an 100x50 array on the free store
 array *r=new array[100];

 delete[] r;

// Creates a 100x50 vector. Prefer this
 vector<vector<int> >s(100, vector<int>(50));

// s clears itself automatically at the end of its scope.
}


catch(std::bad_alloc)
{
 std::cerr<<"I think i saw a catty!\n";
}






>
>
>       for(int i=0;i<nrows;i++)
>          for(int j=0;j<ncolumns;j++)
>            arr[i][j]=0;
>
>       for(int i=0;i<nrows;i++)
>          for(int j=0;j<ncolumns;j++)
>            cout<<arr[i][j]<<" ";
>
>       cout<<sizeof(arr)/sizeof(int)<<endl; //and why does this part
return 
>1
>                                            //instead of 25??


Because it is equivallent of the expresion sizeof(int **)/sizeof(int)
which obviously happen to have the same size.




Ioannis

* Ioannis Vranos
* Programming pages: http://www.noicys.cjb.net
* Alternative URL: http://run.to/noicys