Vector in c++ stl

**dpp** · 05-10-2009

hi...i ve been used to vectors stl
but is it nececssary to mention the size of the vector in the declararion...

can i not leave it unspecified...dynamically increasing as and wen i push items to it....

**anon** · 05-10-2009

Yes, you can.

**laserlight** · 05-10-2009

Originally Posted by dpp

but is it nececssary to mention the size of the vector in the declararion...

No.

Originally Posted by dpp

can i not leave it unspecified...dynamically increasing as and wen i push items to it...

You can indeed increase the size of a std::vector at run time with push_back and other member functions.

**dpp** · 05-10-2009

thanks...then how will my declaration be...with an example plz

**anon** · 05-10-2009

Perhaps post what you have tried? You'll declare an empty vector like any other object with default constructor.

**dpp** · 05-10-2009

simple eg:
vector<long long int>g(1000);

i get error if i use g()

**laserlight** · 05-10-2009

Originally Posted by dpp

i get error if i use g()

It should be:

Code:

vector<long long int> g;

This declares a function named g that takes no arguments and returns a vector:

Code:

vector<long long int> g();

Note that at the moment long long int is not a standard C++ built-in type.

**dpp** · 05-10-2009

thanks...but i dont get it right with normal push_back function....
anythng else needed

**laserlight** · 05-10-2009

Originally Posted by dpp

but i dont get it right with normal push_back function.

That's too bad, I use it and it works.

Originally Posted by dpp

anythng else needed

Yes.

(If you don't get what I am hinting at: post what you tried and state how exactly does it not work.)

**dpp** · 05-10-2009

it works well normally for simple eg....
when i include in my program i get an error....
thanks...
i need to check with it

**Elysia** · 05-10-2009

If you can't get it to work, show the code. We can guess, but we can't be certain and it's by far the fastest and best method of making us give you the help you're looking for.

**dpp** · 05-10-2009

ya ok...say for eg:

Code:

#include<iostream>
#include<vector>
using namespace std;
int main()
{
    int i,j=0;
    //vector<<int>  g;
      vector < vector<long long int> > g;
    while(1)
    {
            j++;
     cin>>i;
     if(i==-1)break;
     g[j].push_back(i);
     }
     return(0);
}

i get runtime error

**laserlight** · 05-10-2009

g is empty so you cannot insert into g[0].

**dpp** · 05-10-2009

ya that is the reasion i used g(maxvalue) in declaration...
but how can i leave it unbounded

**dpp** · 05-10-2009

i want it to be unspecified bound and increasing as and when i push elements....
can i do it...
if so how

Thread: Vector in c++ stl

Thread Tools

Search Thread

Display

Vector in c++ stl

Similar Threads

C Formatting Using STL

im extreamly new help

STL or no STL

Prime Number Generator... Help !?!!

include question