# How to reverse a Vector using STL in C++?

• Difficulty Level : Basic
• Last Updated : 30 May, 2021

Given a vector, reverse this vector using STL in C++.
Example:

```Input: vec = {1, 45, 54, 71, 76, 12}
Output: {12, 76, 71, 54, 45, 1}

Input: vec = {1, 7, 5, 4, 6, 12}
Output: {12, 6, 4, 5, 7, 1}```

Approach: Reversing can be done with the help of reverse() function provided in STL. The Time complexity of the reverse() is O(n) where n is the length of the string.
Syntax:

`reverse(start_index, last_index);`

## CPP

 `// C++ program to reverse Vector` `// using reverse() in STL`   `#include ` `using` `namespace` `std;`   `int` `main()` `{`   `    ``// Get the vector` `    ``vector<``int``> a = { 1, 45, 54, 71, 76, 12 };`   `    ``// Print the vector` `    ``cout << ``"Vector: "``;` `    ``for` `(``int` `i = 0; i < a.size(); i++)` `        ``cout << a[i] << ``" "``;` `    ``cout << endl;`   `    ``// Reverse the vector` `    ``reverse(a.begin(), a.end());`   `    ``// Print the reversed vector` `    ``cout << ``"Reversed Vector: "``;` `    ``for` `(``int` `i = 0; i < a.size(); i++)` `        ``cout << a[i] << ``" "``;` `    ``cout << endl;`   `    ``return` `0;` `}`

Output:

```Vector: 1 45 54 71 76 12
Reversed Vector: 12 76 71 54 45 1```

Time Complexity: O(n) where n is the length of the string.

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