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Rust program to calculate the value of nPr

Given the value of n, r, and we have to calculate the value of nPr using the Rust program.
Last Updated : October 01, 2021

Problem Statement

Here, we will read the value of n and r from the user. Then we will calculate the nPr and print the result.

nPr:

The nPr is the permutation of arrangement of 'r' objects from a set of 'n' objects, into an order or sequence.

The formula to find permutation is: nPr = (n!) / (n-r)!

Program/Source Code

The source code to calculate the value of nPr is given below. The given program is compiled and executed successfully.

// Rust program to calculate the value of nPr

use std::io;

fn getFactorial(num:i32)->i32
{
    let mut f:i32 = 1;
    let mut i:i32 = 1;

    if (num == 0)
    {
        return 1;
    }
    
    while(i <= num) 
    {    
        f = f * i;
        i=i+1;
    }
    return f;
}

fn main() 
{
    let mut n:i32   =0;
    let mut r:i32   =0;
    let mut nPr:i32 =0;
   
    let mut input1 = String::new();
    let mut input2 = String::new();
    
    println!("Enter value of n: ");
    io::stdin().read_line(&mut input1).expect("Not a valid string");
    n = input1.trim().parse().expect("Not a valid number");
    
    println!("Enter value of r: ");
    io::stdin().read_line(&mut input2).expect("Not a valid string");
    r = input2.trim().parse().expect("Not a valid number");

    nPr = getFactorial(n) / getFactorial(n - r);
    println!("The nPr is: {}", nPr);
}

Output

Enter value of n: 
6
Enter value of r: 
4
The nPr is: 360

Explanation

Here, we read the value of n, r from the user. After that, we calculated the nPr and print the result.

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