Interconversion of roman and integer

solution.rs

use std::collections::HashMap;

struct Solution;

impl Solution {
    pub fn int_to_roman(int: i32) -> String {
        let thousands = ["", "M", "MM", "MMM"];
        let hundreds = ["", "C", "CC", "CCC", "CD", "D", "DC", "DCC", "DCCC", "CM"];
        let tens = ["", "X", "XX", "XXX", "XL", "L", "LX", "LXX", "LXXX", "XC"];
        let ones = ["", "I", "II", "III", "IV", "V", "VI", "VII", "VIII", "IX"];

        let mut str_arr = Vec::<&str>::new();

        str_arr.push(thousands[(int as f32 / 1000.0).floor() as usize]);
        str_arr.push(hundreds[((int % 1000) as f32 / 100.0) as usize]);
        str_arr.push(tens[((int % 100) as f32 / 10.0) as usize]);
        str_arr.push(ones[(int % 10) as usize]);

        str_arr.join("").into()
    }

    pub fn roman_to_int(s: String) -> i32 {
        let map = HashMap::<&str, i32>::from([
            ("I", 1),
            ("V", 5),
            ("X", 10),
            ("L", 50),
            ("C", 100),
            ("D", 500),
            ("M", 1000),
        ]);

        let mut romans = s
            .split("")
            .filter(|r| r.len() != 0)
            .map(|r| map.get(r).expect("Unexpected roman char"))
            .collect::<Vec<&i32>>();

        romans.reverse();

        let mut res = romans[0].clone();

        for idx in 1..romans.len() {
            if romans[idx] >= romans[idx - 1] {
                res += romans[idx].clone();
            } else {
                res -= romans[idx].clone();
            }
        }

        res
    }
}