C++ Program to Implement Prev_Permutataion in STL

Prev_permutation in STL is used to rearrange the elements in the range [first, last] into the previous lexicographically smaller permutation. A permutation is each one of the N! possible arrangements the elements can take. Here is a C++ program to implement Prev_permutation in STL.

Algorithm

Begin
   Define one integer array variable elements[].
   Get the number of data e from the user.
   Initialize the array elements[] with e number of data from the keyboard.
   Sort all the array elements.
   Reverse the array elements.
   Do
      show(elements) //to display the current content of the array
      while (prev_permutation(elements, elements + e))
End.

Example Code

#include<iostream>
#include <algorithm>
using namespace std;
void show(int a[], int n) {
   for(int i = 0; i < n; i++) {
      cout<<a[i]<<" ";
   }
   cout<<endl;
}
int main () {
   int e, i;
   cout<<"Enter number of elements to be inserted: ";
   cin>>e;
   int elements[e];
   for (i = 0; i < e; i++) {
      cout<<"Enter "<<i + 1<<" element: ";
      cin>>elements[i];
   }
   sort (elements, elements + e);
   reverse (elements, elements + e);
   cout << "The "<<e<<"! possible permutations with ";
   cout<<e<<" elements: "<<endl;
   do {
      show(elements, e);
   }
   while (prev_permutation(elements, elements + e));
   return 0;
}

Output

Enter number of elements to be inserted: 4
Enter 1 element: 7
Enter 2 element: 6
Enter 3 element: 10
Enter 4 element: 2
The 4! possible permutations with 4 elements:
10 7 6 2
10 7 2 6
10 6 7 2
10 6 2 7
10 2 7 6
10 2 6 7
7 10 6 2
7 10 2 6
7 6 10 2
7 6 2 10
7 2 10 6
7 2 6 10
6 10 7 2
6 10 2 7
6 7 10 2
6 7 2 10
6 2 10 7
6 2 7 10
2 10 7 6
2 10 6 7
2 7 10 6
2 7 6 10
2 6 10 7
2 6 7 10

Nitya Raut

Updated on: 30-Jul-2019

74 Views

Kickstart Your Career

Get certified by completing the course

Get Started