how to reintialize a vector

[zl2k]

hi, there
Suppose I have declared a vector in the header file

vector<int> v1;
vector< vector<int> > v2;

Now I need to reinitialize the vector somewhere later to different
sizes. How can I do that for v2? For v1, I can always say
v1.assign(10,0);
to set its size to 10 and populate with 0s.

For v2, can I reinitialize it with known size of one dimension (row)
and with unknown size of another dimension (collumn)? How? (Or maybe I
can always declare the unknow size to 1 since the vector can grow?)

Thanks ahead.

zl2k

 

[mlimber]

hi, there
Suppose I have declared a vector in the header file

vector<int> v1;
vector< vector<int> > v2;

Now I need to reinitialize the vector somewhere later to different
sizes. How can I do that for v2? For v1, I can always say
v1.assign(10,0);
to set its size to 10 and populate with 0s.

For v2, can I reinitialize it with known size of one dimension (row)
and with unknown size of another dimension (collumn)? How? (Or maybe I
can always declare the unknow size to 1 since the vector can grow?)

Thanks ahead.

zl2k

You can do it in a loop:

v2.resize( newRows );
for( unsigned n=0; n < v2.size(); ++n )
{
v2[ n ].resize( newCols );
}

Or you could do it less efficiently but more concisely:

v2.swap( vector< vector<int> >( newRows, vector<int>( newCols ) );

Cheers! --M

 

[mlimber]

Or you could do it less efficiently but more concisely:

v2.swap( vector< vector<int> >( newRows, vector<int>( newCols ) );

....add an extra closing parenthesis in there.

M