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Rust program to calculate the value of nCr

Given the value or n, r, and we have to calculate the value of nCr 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 nCr and print the result.

nCr:

nCr known as the combination is the method of selection of 'r' objects from a set of 'n' objects where the order of selection does not matter.

To find the value of nCr, we use the formula: nCr = n!/[r!( n-r)!]

Program/Source Code

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

// Rust program to calculate the value of nCr

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 nCr: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");

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

Output

Enter value of n: 
5
Enter value of r: 
3
The nCr is: 10

Explanation

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

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