?
Solved

array in c++

Posted on 2010-08-22
5
Medium Priority
?
305 Views
Last Modified: 2013-11-23
Hi there,

I have 2dim array which have huge number I have no idea about number my question is How can I initialize this array if not are there any different way like array list in Java which is accept two dim and extend automatically
0
Comment
Question by:obad62
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 4
5 Comments
 
LVL 32

Expert Comment

by:phoffric
ID: 33497411
In c++, if you say:
     int arr2d[3][4] = {0};
then every element of the array will be initialized to 0.
0
 
LVL 32

Expert Comment

by:phoffric
ID: 33497412
If you say:
    int arr2d[3][4] = {5};
then arr2d[0][0] will be set to 5, and all the other elements in the array will be set to 0.
0
 
LVL 32

Accepted Solution

by:
phoffric earned 2000 total points
ID: 33497423
If you want to be able to extend an array, then I recommend using vector.
    http://www.cplusplus.com/reference/stl/vector/

There are various ways to construct/initialize a vector.
    http://www.cplusplus.com/reference/stl/vector/vector/

For example:
    vector<int> second (4,100);      // four ints with value 100

Below is the sample code for the vector constructor link.

To extend the array (without worrying about whether it needs extending), you can just add elements to the vector using push_back.
      http://www.cplusplus.com/reference/stl/vector/push_back/
// constructing vectors
#include <iostream>
#include <vector>
using namespace std;

int main ()
{
  unsigned int i;

  // constructors used in the same order as described above:
  vector<int> first;                                // empty vector of ints
  vector<int> second (4,100);                       // four ints with value 100
  vector<int> third (second.begin(),second.end());  // iterating through second
  vector<int> fourth (third);                       // a copy of third

  // the iterator constructor can also be used to construct from arrays:
  int myints[] = {16,2,77,29};
  vector<int> fifth (myints, myints + sizeof(myints) / sizeof(int) );

  cout << "The contents of fifth are:";
  for (i=0; i < fifth.size(); i++)
    cout << " " << fifth[i];

  cout << endl;

  return 0;
}

Open in new window

0
 
LVL 32

Expert Comment

by:phoffric
ID: 33497440
Above was a 1D discussion of vectors. Here's a thread needing a 2D vector:
     http://w.e-e.com/pJzEMB
0
 
LVL 40

Expert Comment

by:evilrix
ID: 33498588
If you want a simple 2D array, Boost's ublas library offers a simple to use matrix.
http://www.boost.org/doc/libs/1_38_0/libs/numeric/ublas/doc/matrix.htm

If you matrix is huge it is worth considering the sparse version.
http://www.boost.org/doc/libs/1_38_0/libs/numeric/ublas/doc/matrix_sparse.htm
0

Featured Post

What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

This article will show you some of the more useful Standard Template Library (STL) algorithms through the use of working examples.  You will learn about how these algorithms fit into the STL architecture, how they work with STL containers, and why t…
Jaspersoft Studio is a plugin for Eclipse that lets you create reports from a datasource.  In this article, we'll go over creating a report from a default template and setting up a datasource that connects to your database.
The viewer will learn how to use NetBeans IDE 8.0 for Windows to connect to a MySQL database. Open Services Panel: Create a new connection using New Connection Wizard: Create a test database called eetutorial: Create a new test tabel called ee…
The viewer will be introduced to the technique of using vectors in C++. The video will cover how to define a vector, store values in the vector and retrieve data from the values stored in the vector.
Suggested Courses

752 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question