// 近日閒暇練練 Rust 興許以後寫分散式系統的時候會和它打交道呢

use std::collections::HashMap;

impl Solution {
        pub fn is_valid(s: String) -> bool {
                let pairs: HashMap<char, char> = [ 
                        ('(', ')'),
                        ('[', ']'),
                        ('{', '}'),
                ].iter().cloned().collect();

                let mut stack: Vec<char> = vec![];
                for c in s.chars() {
                        if pairs.contains_key(&c) {
                                stack.push(c)
                        } else if stack.pop().and_then(|k| pairs.get(&k)).unwrap_or(&'#') != &c { 
                                return false;
                        }   
                }   

                stack.is_empty()
        }   
}