Question

How to find all the strong numbers in a given range with Rust

Answer 1

// Strong numbers are the numbers that the sum of factorial of its digits 
// is equal to the original number
    
// 145 is a strong number: 1 + 24 + 120 = 145

fn factorial(n: i32) -> i32 {
    let mut fact = 1;
    for i in 2..=n {
        fact *= i;
    }
    fact
}

fn main() {
    for n in 1..=1_000_000 {
        let mut tmp = n;
        let mut sum = 0;
        while tmp != 0 {
            let reminder = tmp % 10;
            sum += factorial(reminder);
            tmp /= 10;
        }
        if sum == n {
            println!("{}", n);
        }
    }
}



/*
run:

1
2
145
40585

*/

 

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