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

        // Create a HashSet to store characters of the current substring.
        let mut char_set = HashSet::new();
        // Convert the string to a vector of chars to easily access characters by index.
        let chars: Vec<char> = s.chars().collect();
        // Initialize variables for the maximum length found and the left pointer of the window.
        let mut max_length = 0;
        let mut left = 0;

        // Iterate through the string with the right pointer (i).
        for right in 0..chars.len() {
            // Check if the character at the right pointer is already in the set.
            // If it is, remove characters from the left until it's not, effectively sliding the window.
            while char_set.contains(&chars[right]) {
                char_set.remove(&chars[left]);
                left += 1;
            }

            // Add the current character to the set.
            char_set.insert(chars[right]);

            // Calculate the length of the current substring and update max length if necessary.
            max_length = std::cmp::max(max_length, right - left + 1);
        }

        // Return the maximum length found.
        max_length as i32
    }
}