Initialize a vector in C++ (5 different ways)

Following are different ways to create and initialize a vector in C++ STL

Initializing by pushing values one by one :

filter_none

edit
close

play_arrow

link
brightness_4
code

// CPP program to create an empty vector
// and push values one by one.
#include <bits/stdc++.h>
using namespace std;
  
int main()
{
    // Create an empty vector
    vector<int> vect; 
     
    vect.push_back(10);
    vect.push_back(20);
    vect.push_back(30);
  
    for (int x : vect)
        cout << x << " ";
  
    return 0;
}

chevron_right


Output:

10 20 30

Specifying size and initializing all values :

filter_none

edit
close

play_arrow

link
brightness_4
code

// CPP program to create an empty vector
// and push values one by one.
#include <bits/stdc++.h>
using namespace std;
  
int main()
{
    int n = 3;
  
    // Create a vector of size n with
    // all values as 10.
    vector<int> vect(n, 10);
  
    for (int x : vect)
        cout << x << " ";
  
    return 0;
}

chevron_right


Output:



10 10 10

Initializing like arrays :

filter_none

edit
close

play_arrow

link
brightness_4
code

// CPP program to initialize a vector like
// an array.
#include <bits/stdc++.h>
using namespace std;
  
int main()
{
    vector<int> vect{ 10, 20, 30 };
  
    for (int x : vect)
        cout << x << " ";
  
    return 0;
}

chevron_right


Output:

10 20 30

Initializing from an array :

filter_none

edit
close

play_arrow

link
brightness_4
code

// CPP program to initialize a vector from
// an array.
#include <bits/stdc++.h>
using namespace std;
  
int main()
{
    int arr[] = { 10, 20, 30 };
    int n = sizeof(arr) / sizeof(arr[0]);
  
    vector<int> vect(arr, arr + n);
  
    for (int x : vect)
        cout << x << " ";
  
    return 0;
}

chevron_right


Output:

10 20 30

Initializing from another vector :

filter_none

edit
close

play_arrow

link
brightness_4
code

// CPP program to initialize a vector from
// another vector.
#include <bits/stdc++.h>
using namespace std;
  
int main()
{
    vector<int> vect1{ 10, 20, 30 };
  
    vector<int> vect2(vect1.begin(), vect1.end());
  
    for (int x : vect2)
        cout << x << " ";
  
    return 0;
}

chevron_right


Output:

10 20 30

This article is contributed by Kartik. If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above.

Don’t stop now and take your learning to the next level. Learn all the important concepts of Data Structures and Algorithms with the help of the most trusted course: DSA Self Paced. Become industry ready at a student-friendly price.




My Personal Notes arrow_drop_up

Article Tags :
Practice Tags :


68


Please write to us at contribute@geeksforgeeks.org to report any issue with the above content.