use std::collections::HashMap; pub fn brackets_are_balanced(string: &str) -> bool { Brackets::from(string).are_balanced() } struct Brackets { raw_brackets: Vec, pairs: MatchingBrackets, } impl From<&str> for Brackets { fn from(i: &str) -> Self { Brackets::new(i, None) } } impl Brackets { fn new(s: &str, pairs: Option>) -> Self { let p = match pairs { Some(x) => MatchingBrackets::from(x), None => MatchingBrackets::from(vec![('[', ']'), ('{', '}'), ('(', ')')]), }; Brackets { raw_brackets: s.chars().filter(|c| p.contains(c)).collect::>(), pairs: p, } } fn are_balanced(&self) -> bool { let mut unclosed: Vec = Vec::new(); for &bracket in self.raw_brackets.iter() { if let Some(last_unclosed) = unclosed.pop() { unclosed.extend(self.pairs.unmatched(last_unclosed, bracket)); } else { unclosed.push(bracket); } } unclosed.is_empty() } } struct MatchingBrackets { collection: HashMap, } impl From> for MatchingBrackets { fn from(v: Vec<(char, char)>) -> Self { MatchingBrackets { collection: v.into_iter().collect::>(), } } } impl MatchingBrackets { fn contains(&self, other: &char) -> bool { self.collection .iter() .any(|(k, v)| k == other || v == other) } fn closer_for(&self, k: &char) -> Option<&char> { self.collection.get(k) } fn closed_by(&self, l: char, r: char) -> bool { match self.closer_for(&l) { Some(&x) => r == x, None => false, } } fn unmatched(&self, open: char, potential_close: char) -> Vec { let mut ret: Vec = Vec::new(); if !self.closed_by(open, potential_close) { ret.push(open); ret.push(potential_close); } ret } }