question for returning an array

[=?iso-8859-9?B?RGlu52F5IEFr5/ZyZW4=?=]

Following function

void mdelr(int *ar1, int a, int b, int d )
{
int i,j,tmp;
int *temp;
for (i=0; i<a; i++)
{
for(j=0; j<b; j++)
{
if (i >= d)
ar1[i*b+j] = ar1[(i+1)*b+j];
if (i == b-1)
ar1[i*b+j] = 0;
}
}
tmp = ar1[0];
temp = new int[(a-1)*b];
for(i=0; i<b*a-b; i++)
temp[i] = ar1[i];
delete ar1;
ar1 = temp;
cout << "\last version of array" << d << " " << tmp << "\n";
for (i=0; i<a-1; i++)
{
for(j=0; j<b; j++)
{
cout << ar1[i*b +j] << " ";
}
cout << "\n";
}

}
and following main block

int main(void)
{
int *ar1,*ar2;
int i,j,k;
int temp, sayi,ROW,COL;
int *pt;
ROW=COL=5;
ar1 = new int[ROW*COL];
cout << "row number to be deleted";
cin >sayi;
pt = new int[sayi];
for(i=0; i<sayi; i++)
{
cout << "Enter col num" << i;
cin >temp;
temp--;
pt[i] = temp-i;
}
for(i=0; i<sayi; i++)
cout << pt[i] << " ";
cout << "\n";
system("pause") ;
/*assign values*/
for (i=0;i<ROW;i++)
{
for(j=0;j<COL;j ++)
{
ar1[i*COL +j] = (i+i+j+1);
}
}
cout << "original matrix\n";
for (i=0; i<ROW; i++)
{
for(j=0; j<COL; j++)
{
cout << ar1[i*ROW +j] << " ";
}
cout << "\n";
}
for(k=0; k<sayi; k++)
{
cout << "step " << k << "\n";
mdelr(ar1,ROW-k,COL,pt[k]);
cout << "\nresult in main" << k << "\n";
for (i=0; i<ROW-k-1; i++)
{
for(j=0; j<COL; j++)
{
cout << ar1[i*(COL) +j] << " ";
}
cout << "\n";
}
}
delete ar1;
delete pt;
system("pause") ;
return 0;

}
gives the following output

row number to be deleted 2
Enter col num02
Enter col num14
1 2
Devam etmek için bir tusa bas n . . .
original matris
1 2 3 4 5
3 4 5 6 7
5 6 7 8 9
7 8 9 10 11
9 10 11 12 13
step 0
last version of array1 1
1 2 3 4 5
5 6 7 8 9
7 8 9 10 11
9 10 11 12 13
result in main 0
0 2 3 4 5
5 6 7 8 9
7 8 9 10 11
9 10 11 12 13
adim 1
last version of array2 0
0 2 3 4 5
5 6 7 8 9
9 10 11 12 13
result in main 1
4007120 2 3 4 5
5 6 7 8 9
9 10 11 12 13
Devam etmek için bir tusa bas n . . .
My question is why the first element of the array becomes stupid
despite all of my effords? I believe returning to main changes the
first element but I cannot prevent this.

[=?ISO-8859-9?Q?Erik_Wikstr=F6m?=]

On 2007-09-02 10:50, Dinçay Akçören wrote:

Following function

void mdelr(int *ar1, int a, int b, int d )
{
int i,j,tmp;
int *temp;
for (i=0; i<a; i++)
{
for(j=0; j<b; j++)
{
if (i >= d)
ar1[i*b+j] = ar1[(i+1)*b+j];
if (i == b-1)
ar1[i*b+j] = 0;
}
}
tmp = ar1[0];
temp = new int[(a-1)*b];
for(i=0; i<b*a-b; i++)
temp[i] = ar1[i];
delete ar1;
ar1 = temp;

This will not change what ar1 points to in main() since you passed a
copy of the pointer. You need to pass the pointer by reference:

void mdelr(int *&ar1, int a, int b, int d )

--
Erik Wikström

[BobR]

Dinçay Akçören <di****@gmail.c omwrote in message...

>Following function

Are you comeing from a 'C' background?

void mdelr(int *ar1, int a, int b, int d ){
int i,j,tmp;
int *temp;

Why are those there, and un-initialized?
You don't use 'i' or 'j' outside the loops, so, let's rewrite that to be
more C++ like...

int* mdelr( int *ar1, int a, int b, int d ){
for( int i(0); i < a; ++i ){
for( int j(0); j < b; ++j ){
if( i >= d ) ar1[i*b+j] = ar1[(i+1)*b+j];
if( i == b-1 ) ar1[i*b+j] = 0;
} // for(j)
} // for(i)
int *temp( new int[(a-1)*b] );
for( int i(0); i < b*a-b; ++i )
temp[i] = ar1[i];
using std::cout;
cout << "\nlast version of array" << d << " " << ar1[0] << "\n";
delete [] ar1;
ar1 = temp;
delete [] temp;

for( int i(0); i < a-1; ++i){
for( int j(0); j < b; ++j){
cout << ar1[i*b +j] << " ";
}
cout << "\n";
}
return ar1;
} // mdelr(int*,int, int,int)

and following main block

// int main(void)
int main(){ // C++
using std::cout;
// int *ar1,*ar2;
// int i,j,k;
// int temp, sayi,ROW,COL;
// int *pt;

Why are those there, and un-initialized?

// ROW=COL=5;
Reserve all-caps for macros.

size_t Row(5), Col(5);

// ar1 = new int[ROW*COL];
int *ar1( new int[ Row * Col ] );

cout << "row number to be deleted";

int sayi(0);

cin >sayi;

// pt = new int[sayi];
int *pt( new int[ sayi ] );

int temp(0);
// for(i=0; i<sayi; i++){
for( int i(0); i < sayi; ++i){

cout << "Enter col num" << i;
cin >temp;

How do you know input succeeded?

temp--;
pt[i] = temp-i;
}

You fix the rest...

// in for(k)
// mdelr(ar1,ROW-k,COL,pt[k]);

ar1 = mdelr( ar1, Row-k, Col, pt[k] );

// delete ar1;
// delete pt;
delete [] ar1;
delete [] pt;

system("pause") ;
return 0;
} // main()

My question is why the first element of the array becomes stupid
despite all of my effords? I believe returning to main changes the
first element but I cannot prevent this.

What Erik and Alf said.

To get you going, I'll give you a short example using std::vector.
// ------------
#include <iostream>
#include <vector>

void FillVector( std::vector< int &vec){ // non-const here
vec.push_back( 1 );
vec.push_back( 2 );
vec.push_back( 3 );
// vec.at(0) = 42; // change 1 to 42 in first element.
return;
} // FillVector(vect or<int>&)

void PrintVector( std::vector< int const &vec, // const here
std::ostream &out ){
for( std::size_t i(0); i < vec.size(); ++i ){
out<<vec.at(i)< <std::endl;
// or: out<<vec[ i ]<<std::endl;
}
// I won't show the std::copy method here.
// Look it up, or review this NG for it.
return;
} // PrintVector(vec tor<int>const&, ostream&)

int main(){
std::vector< int MyVec;
FillVector( MyVec );
PrintVector( MyVec, std::cout );
return 0;
} // main()
// ------------

You can initialize the vector:

// std::vector< int MyVec( 25 );
std::vector< int MyVec( 25, 7 );

.....will give you a vector with 25 elements, all set to '7'.
Read-up on std::vector for much more.

--
Bob R
POVrookie