# All Permutations Of An Array In C++

In this tutorial, we shall learn to compute all permutations of an array in C++. Here we shall be using STL’s next_permutation function. The std::next_permutation is used to rearrange the elements in the range [first, last) into the next lexicographically greater permutation.

A permutation is defined as each one of the possible arrangements that can be made in factorial N ways.

The permutation is ordered lexicographically to each other. Its syntax is:

bool next_permutation (BidirectionalIterator first, BidirectionalIterator last);

## Permutations Of An Array

The display function takes two arguments first one is an array and the next is its size. Similarly, the Find_Permtations function takes an array and next is its size. We have also used the std::sort which will sort the array from index a to index a+n that is from index 0 to the last index of the array. Sorting is done to get the numbers in lexicographical order starting from the first number.

#include <bits/stdc++.h> typedef long long ll; // Macro for long long using namespace std; void display(ll* , ll) ; // Function for displaying the array void Find_Permutations(ll* , ll ) ; // Function to find the permutations of array int main() { ll a[] = { 1, 2, 3, 4 }; ll n = sizeof(a) / sizeof(a[0]); Find_Permutations(a, n); return 0; } void display(ll a[], ll n) { for (ll i = 0; i < n; i++) { cout << a[i] << " "; } cout << endl; } void Find_Permutations(ll a[], ll n) { // Sort the given array sort(a, a + n); // Find all possible permutations cout << "Possible permutations are:\n"; do { display(a, n); } while (next_permutation(a, a + n)); }

It will produce the output:

Possible permutations are: 1 2 3 4 1 2 4 3 1 3 2 4 1 3 4 2 1 4 2 3 1 4 3 2 2 1 3 4 2 1 4 3 2 3 1 4 2 3 4 1 2 4 1 3 2 4 3 1 3 1 2 4 3 1 4 2 3 2 1 4 3 2 4 1 3 4 1 2 3 4 2 1 4 1 2 3 4 1 3 2 4 2 1 3 4 2 3 1 4 3 1 2 4 3 2 1

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