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

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

Initializing by one by one pushing values :

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// 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;
}

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Output:



10 20 30

Specifying size and initializing all values :

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// 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;
}

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Output:

10 10 10

Initializing like arrays :

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// 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;
}

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Output:

10 20 30

Initializing from array :

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// 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;
}

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Output:

10 20 30

Initializing from another vector :

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// 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;
}

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Output:

10 20 30

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