Question

How to sum the digits of the number 2^N in Rust

Answer 1

use num_bigint::BigUint;

fn sum_of_digits(n: u32) -> u32 {
    // Compute 2^n using BigUint
    let two = BigUint::from(2u32);
    let power = two.pow(n);

    // Convert to string and sum digits
    power
        .to_string()
        .chars()
        .map(|c| c.to_digit(10).unwrap())
        .sum()
}

fn main() {
    for &n in &[15, 100, 1000] {
        println!("Sum of digits of 2^{} is: {}", n, sum_of_digits(n));
    }
}



    
/*
run:

Sum of digits of 2^15 is: 26
Sum of digits of 2^100 is: 115
Sum of digits of 2^1000 is: 1366
   
*/

 

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