impl Solution {
    fn roman_to_int(s: String) -> i32 {
        use std::collections::HashMap;

        // Step 1: Define the mapping of Roman numerals to integers
        let mut roman_values = HashMap::new();
        roman_values.insert('I', 1);
        roman_values.insert('V', 5);
        roman_values.insert('X', 10);
        roman_values.insert('L', 50);
        roman_values.insert('C', 100);
        roman_values.insert('D', 500);
        roman_values.insert('M', 1000);

        // Initialize a variable to store the result
        let mut result = 0;

        // Convert the input string to a vector of characters
        let chars: Vec<char> = s.chars().collect();

        // Iterate over the characters in the input string
        for i in 0..chars.len() {
            // If the current character is less than the next one, subtract its value from the result
            if i + 1 < chars.len() && roman_values[&chars[i]] < roman_values[&chars[i + 1]] {
                result -= roman_values[&chars[i]];
            } else {
                // Otherwise, add its value to the result
                result += roman_values[&chars[i]];
            }
        }

        // Return the result
        result
    }
}