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use std::fs;
use std::path::Path;
use std::collections::HashMap;
use lazy_static::lazy_static;
lazy_static! {
static ref SCORE1: HashMap<u8,u32> = {
let mut m = HashMap::new();
m.insert(b')', 3);
m.insert(b']', 57);
m.insert(b'}', 1197);
m.insert(b'>', 25137);
m
};
static ref SCORE2: HashMap<u8,u64> = {
let mut m = HashMap::new();
m.insert(b')', 1);
m.insert(b']', 2);
m.insert(b'}', 3);
m.insert(b'>', 4);
m
};
}
/* AOC21 Day 10: https://adventofcode.com/2021/day/10 */
fn main() {
let input = Path::new("resources").join("input.txt");
let content = fs::read_to_string(input).expect("Unable to read input file");
ex1(&content);
ex2(&content);
}
fn ex1(content: &str) {
let ex1: u32 =
content.lines()
.filter_map(|l| check_line(l).err())
.sum();
println!("Ex1: the result is {}", ex1);
}
fn ex2(content: &str) {
let mut ex2: Vec<u64> =
content.lines()
.filter_map(|l| check_line(l).ok())
.map(|v| v.iter().rev().fold(0, |a,p| a*5 + SCORE2.get(p).unwrap()))
.collect();
ex2.sort();
println!("Ex2: the result is {}", ex2[ex2.len()/2]);
}
fn check_line(line: &str) -> Result<Vec<u8>,u32> {
let acc = Ok(Vec::with_capacity(line.len()));
line.bytes().fold(acc, |a,c| match a {
Ok(mut a) => {
match c {
b'(' => { a.push(b')'); Ok(a) },
b'[' | b'{' | b'<' => { a.push(c+2); Ok(a) },
b')' | b']' | b'}' | b'>' =>
if a.pop().filter(|&x| x == c).is_some() {
Ok(a)
} else {
Err(*SCORE1.get(&c).unwrap())
},
_ => unreachable!()
}
},
Err(_) => a
})
}
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