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use advent_lib::prelude::*;
use std::collections::BTreeMap;
use std::collections::BTreeSet;
#[derive(Clone,Debug)]
struct Range {
min: i64,
max: i64,
}
fn main() -> Result<()> {
let mut args = std::env::args();
if args.len() != 2 {
eprintln!("Usage: advent input");
}
let _ = args.next();
let filename = args.next().unwrap();
let input = advent_lib::read_lines_file(&filename)?;
let input = advent_lib::group_lines_by_blanks(input);
let mut rules: BTreeMap<String,Vec<Range>> = BTreeMap::new();
for line in &input[0] {
let colon_point = line.find(':').unwrap();
let (field_name, rest) = line.split_at(colon_point);
let (_, rest) = rest.split_at(2);
let mut ranges: Vec<Range> = Vec::new();
for word in rest.split(' ') {
if word == "or" {
continue;
}
let parts: Vec<&str> = word.split('-').collect();
ranges.push(Range {
min: parts[0].parse::<i64>().unwrap(),
max: parts[1].parse::<i64>().unwrap(),
});
}
rules.insert(field_name.to_string(), ranges);
}
let player_ticket = parse_comma_separated_ints(&input[1][1]);
let mut nearby_tickets = Vec::new();
for line in input[2].iter().skip(1) {
nearby_tickets.push(parse_comma_separated_ints(&line));
}
let mut valid_tickets = Vec::new();
valid_tickets.push(player_ticket.clone());
let mut error_sum = 0;
for ticket in &nearby_tickets {
let mut is_valid = true;
for value in ticket {
let mut found_match = false;
for rule in rules.values() {
if value_obeys_rule(*value, rule) {
found_match = true;
break;
}
}
if !found_match {
error_sum += value;
is_valid = false;
}
}
if is_valid {
valid_tickets.push(ticket.clone());
}
}
println!("{}", error_sum);
let mut possibilities: Vec<BTreeSet<String>> = Vec::new();
for _ in 0 .. player_ticket.len() {
let mut all_fields = BTreeSet::new();
for field_name in rules.keys() {
all_fields.insert(field_name.clone());
}
possibilities.push(all_fields);
}
for ticket in valid_tickets {
//println!("{:?}", possibilities);
for i in 0 .. ticket.len() {
let mut fields_to_remove = Vec::new();
for field_name in possibilities[i].iter() {
let rule = rules.get(field_name).unwrap();
if !value_obeys_rule(ticket[i], rule) {
/*
println!("{}: value {} does not obey rule for {}",
i, ticket[i], field_name);
*/
fields_to_remove.push(field_name.clone());
}
}
for field_name in fields_to_remove {
possibilities[i].remove(&field_name);
}
}
}
//println!("{:?}", possibilities);
let mut finalized_fields = BTreeSet::new();
loop {
let mut removed_any = false;
for i in 0 .. player_ticket.len() {
let mut unique_field = None;
if possibilities[i].len() == 1 {
let field_name = possibilities[i].iter().next().unwrap().clone();
if finalized_fields.contains(&field_name) {
continue;
}
unique_field = Some((i, field_name));
}
match unique_field {
Some((i_to_skip, field_name)) => {
removed_any = true;
for j in 0 .. possibilities.len() {
if j == i_to_skip {
continue;
}
possibilities[j].remove(&field_name);
}
finalized_fields.insert(field_name);
},
None => { },
}
}
if !removed_any {
break;
}
}
let mut product = 1;
for i in 0 .. possibilities.len() {
let field_name = possibilities[i].iter().next().unwrap();
if field_name.starts_with("departure ") {
product *= player_ticket[i];
}
}
println!("{}", product);
Ok(())
}
fn parse_comma_separated_ints(line: &str) -> Vec<i64> {
let mut result = Vec::new();
for word in line.split(',') {
result.push(word.parse::<i64>().unwrap());
}
result
}
fn value_obeys_rule(value: i64, rule: &Vec<Range>) -> bool {
for range in rule {
if value >= range.min && value <= range.max {
return true;
}
}
false
}
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