Kertoma

use std::io;

fn main() {
    let mut occurrences: Vec<u32> = Vec::with_capacity(10);
    let mut number_count: u32 = 0;
    {
        let mut inputline = String::new();
        io::stdin().read_line(&mut inputline).unwrap();
        for value in inputline.split_whitespace() {
            if let Ok(count) = value.parse::<u32>() {
                occurrences.push(count);
                number_count += count;
            }
        }
    }

    println!("{}", if number_count < 4 { small(&occurrences) } else { big(number_count) });
}

fn small(occurrences: &Vec<u32>) -> u32 {
    let mut factorial = 2;
    for i in 3..7 {
        if is_answer(factorial, occurrences) {
            return i-1;
        }
        factorial *= i;
    }
    0
}

fn big(number_count: u32) -> u32 {
    let n = (number_count - 1) as f64;
    let mut i = 6;
    let mut log = 2.85733249643126846023;
    while log <= n {
        i += 1;
        log += (i as f64).log10();
    }
    i
}

fn is_answer(mut factorial: u32, occurrences: &Vec<u32>) -> bool {
    let mut occurrences = occurrences.to_vec();
    while factorial > 0 {
        let num = (factorial % 10) as usize;
        if occurrences[num] <= 0 { return false; }
        occurrences[num] -= 1;
        factorial /= 10;
    }
    for count in occurrences {
        if count != 0 { return false; }
    }
    true
}

Test 1

Group: 1, 2, 3

Verdict: ACCEPTED

Test 2

Group: 1, 2, 3

Verdict: ACCEPTED

Test 3

Group: 1, 2, 3

Verdict: ACCEPTED

Test 4

Group: 1, 2, 3

Verdict: ACCEPTED

Test 5

Group: 1, 2, 3

Verdict: ACCEPTED

Test 6

Group: 1, 2, 3

Verdict: ACCEPTED

Test 7

Group: 2, 3

Verdict: ACCEPTED

Test 8

Group: 2, 3

Verdict: ACCEPTED

Test 9

Group: 2, 3

Verdict: ACCEPTED

Test 10

Group: 2, 3

Verdict: ACCEPTED

Test 11

Group: 3

Verdict: ACCEPTED

Test 12

Group: 3

Verdict: ACCEPTED

Test 13

Group: 3

Verdict: ACCEPTED

Test 14

Group: 3

Verdict: ACCEPTED

Test 15

Group: 3

Verdict: ACCEPTED

Test 16

Group: 3

Verdict: ACCEPTED