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 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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