matching brackets rust code. Attempt #2

attempt_3.rs

pub fn brackets_are_balanced(string: &str) -> bool {
    // second attempt/idea:
    //  push opening brace onto array
    //  pop array on close and check for match
    //  pop on empty => false
    //  not empty at end => false
    // third attempt:
    //  make a hashmap of open/close remove code duplication in the
    //  close bracket logic
    //  Is this really the best way to make a fixed hashmap?  Also, we
    //  build it everytime.

    let mut found = Vec::new();

    // create a hashmap from a fixed list of of open/close pairs
    // Map{close}=open
    let opening_bracket: std::collections::HashMap<char, char> =
        [('[', ']'), ('{', '}'), ('(', ')')]
            .iter()
            .cloned()
            .map(|(a, b)| (b, a))
            .collect();

    // println!("{:?}", opening_bracket);

    for c in string.chars() {
        match c {
            '{' | '(' | '[' => found.push(c),
            '}' | ')' | ']' => match (found.pop(), opening_bracket.get(&c)) {
                (Some(open), Some(&exp_open)) => {
                    if open != exp_open {
                        return false;
                    }
                }
                (_, _) => return false,
            },
            _ => (),
        }
    }
    found.is_empty()
}

matching_brackets.rs

pub fn brackets_are_balanced(string: &str) -> bool {                                     
    // second attempt/idea:
    //  push opening brace onto array
    //  pop array on close and check for match
    //  pop on empty => false
    //  not empty at end => false

    let mut found = Vec::new();

    for c in string.chars() {
        match c { 
            '{' | '(' | '[' => found.push(c),
            ']' => match found.pop() {
                Some('[') => (), 
                _ => return false,
            },  
            ')' => match found.pop() {
                Some('(') => (), 
                _ => return false,
            },  
            '}' => match found.pop() {
                Some('{') => (), 
                _ => return false,
            },  
            _ => (), 
        }   
    }   
    found.is_empty()
}