What is the correct way to initialize vector in?

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

1. Initializing by pushing values one by one :

CPP

#include <iostream>

#include <vector>

using namespace std;

int main()

{

    vector<int> vect;

    vect.push_back(10);

    vect.push_back(20);

    vect.push_back(30);

    for (int x : vect)

        cout << x << " ";

    return 0;

}

2. Specifying size and initializing all values :

CPP

#include <iostream>

#include <vector>

using namespace std;

int main()

{

    int n = 3;

    vector<int> vect(n, 10);

    for (int x : vect)

        cout << x << " ";

    return 0;

}

3. Initializing like arrays :

CPP

#include <iostream>

#include <vector>

using namespace std;

int main()

{

    vector<int> vect{ 10, 20, 30 };

    for (int x : vect)

        cout << x << " ";

    return 0;

}

4. Initializing from an array :

CPP

#include <iostream>

#include <vector>

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;

}

5. Initializing from another vector :

CPP

#include <iostream>

#include <vector>

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;

}

6. Initializing all elements with a particular value :

CPP

#include <iostream>

#include <vector>

using namespace std;

int main()

{

    vector<int> vect1(10);

    int value = 5;

    fill(vect1.begin(), vect1.end(), value);

    for (int x : vect1)

        cout << x << " ";

}

Output

5 5 5 5 5 5 5 5 5 5 

7. Initialize an array with consecutive numbers using std::iota :

C++

#include <iostream>

#include <numeric>

using namespace std;

int main()

{

    int arr[5];

    iota(arr, arr + 5, 1);

    for (int i = 0; i < 5; i++) {

        cout << arr[i] << " ";

    }

    return 0;

}

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