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

https://www.geeksforgeeks.org/initialize-a-vector-in-cpp-different-ways/

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

Initializing by one by one pushing values :

// CPP program to create an empty vector

// and one by one push values.

#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;

}

Output:

10 20 30

Specifying size and initializing all values :

// CPP program to create an empty vector

// and one by one push values.

#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;

}

Output:

10 10 10

Initializing like arrays :

// CPP program to initialize a vector like

// array.

#include <bits/stdc++.h>

using namespace std;

 

int main()

{

    vector<int> vect{ 10, 20, 30 };

 

    for (int x : vect)

        cout << x << " ";

 

    return 0;

}

Output:

10 20 30

Initializing from array :

// CPP program to initialize a vector from

// 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;

}

Output:

10 20 30

Initializing from another vector :

// 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(), vect.end());

 

    for (int x : vect2)

        cout << x << " ";

 

    return 0;

}

Output:

10 20 30