# Permutations in which n people can occupy r seats in a classroom in java

## Java Program to find the Permutations in which n people can occupy r seats in a classroom

Our Aim is to write a Java code to find all the possible permutations in which (n) people can occupy (r) number of seats in a classroom.

Suppose (n) number  students are looking to find (r) seats in a classroom so how will they do it . They will do it with simple formula which is given by

nPr =    n! / (n-r)!

Example :

5P2 means a permutation of 5 things taken 2 at a time. Start with the first number (which in this case is 5), and count down for a total of 2 numbers: 5P2 = 5*4 = 20. #### Implementation:

•  Start
•  Ask the user to input n number of people and the number of seats as r.
•  Calculate permutation p(n,r).
•  Calculate permutation by using formula P(n,r) = n! / (n-r)!
• Print the calculated result.
•  End #### Java code :

`import java.util.*;  import java.io.*;    class PrepInsta    {        public static void main(String[] args)          {              int n, r, per, fact1, fact2;              Scanner sc =  new Scanner(System.in);              System.out.println("Enter the Value of n and r");              n = sc.nextInt();              r = sc.nextInt();              fact1 = n;              for (int i = n - 1; i >= 1; i=i-1)              {                  fact1 = fact1 * i;  //calculating factorial (n!)            }              int number;              number = n - r;              fact2 = number;              for (int i = number - 1; i >= 1; i=i-1)              {                  fact2 = fact2 * i;  //calculating factorial ((n-r)!)            }              per = fact1 / fact2;  //calculating  nPr            System.out.println(per+"ways");      }  }  `
`Output:`
```Enter the Value of n and r
5
220 ways```