The **`random_shuffle()` function** in C++ is used to randomly shuffle elements within a specified range.

This function is available in the `<algorithm.h>` header file.

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## Parameters

The `random_shuffle()` function accepts the following parameters:
* **`first`**: an iterator that points to the first index of the array or vector from which we want to randomly shuffle the elements.
* **`last`**: an iterator that points to the last index of the array or vector until which we want to rotate the elements.
* **`gen`**: an optional parameter that specifies a unary function, which tells how to shuffle the elements.

## Return value

The `random_shuffle()` function does not return any value.

## Code
Let’s look at the code to understand it better.


#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;

int main() {
  vector<int> vec = {1,2,3,4,5,6,7,8,9};
  
  random_shuffle(vec.begin(), vec.end());
  
  cout << "Updated vector: ";
  for (int x: vec)
    cout << x << " ";

  return 0;
}

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## Explanation
* From _lines 1 to 3_, we import the required libraries.
* In _line 7_, we create a vector containing integer values.
* In _line 9_, we call the `random_shuffle()` function and pass the required parameters.
* Finally, from _lines 11 to 13_, we print the randomly shuffled vector.

In this way, we can use the `random_shuffle()` function to randomly shuffle elements in C++.

How to use the random_shuffle() function in C++

In C++, random_shuffle() randomly shuffles elements within a specified range using iterators and an optional unary function.