The **`next_permutation()` function** is available under the `<algorithm.h>` header file in `C++`. 

This function rearranges the elements into the next #key# lexicographical: a generalization of the alphabetical order of the dictionaries #key# greater #key# permutation: possible ways in which a number of things can be reordered or arranged #key#. 

For example, if you have the elements `[1, 2, 3]`, the next greater lexicographical permutation will be `[1, 3, 2]`.

# Parameters

The `next_permutation()` accepts the following parameters:

* **`first`:** This is the start position of your search space. It is an iterator that usually points to the start of an `array`.

* **`last`:** This is the end position of your search space. It is an iterator that usually points to the last position of an `array`.

* **`comp`:** This is an optional parameter that specifies the custom condition to swap the elements and create the next permutation.

# Return type

The `next_permutation()` function returns `true` when it rearranges the elements in the next greater lexicographical permutation. 

It swaps the elements in place. That means it will create the next permutation and store it back in the same `array`.

This way, you will lose your original `array` but you will not use up extra space.

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

int main () {
  int myints[] = {1,2,3};

  next_permutation(myints, myints + 3);
  
  for(int x: myints)
    cout << x << " ";

  return 0;
}

# Explanation

* In _line 6_, we create an `array` of integers.

* In _line 8_, we call the `next_permutation()` function.

* Finally, in _line 11_, we print the next greater permutation.

This way, you can also run a loop to find all the permutations and check whether the `next_permutation()` function returns `true` or not.

What is the next_permutation() function in C++?

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