# Initialize a vector in C++ (6 different ways)

• Difficulty Level : Easy
• Last Updated : 04 Feb, 2021

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

1. Initializing by pushing values one by one :

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## CPP

 `// CPP program to create an empty vector``// and push values one by one.``#include ``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`

2. Specifying size and initializing all values :

## CPP

 `// CPP program to create an empty vector``// and push values one by one.``#include ``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`

3. Initializing like arrays :

## CPP

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

Output:

`10 20 30`

4. Initializing from an array :

## CPP

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

Output:

`10 20 30`

5. Initializing from another vector :

## CPP

 `// CPP program to initialize a vector from``// another vector.``#include ``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;``}`

Output:

`10 20 30`

6. Initializing all elements with a particular value :

## CPP

 `#include ``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`

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