103 lines
3.5 KiB
Rust
103 lines
3.5 KiB
Rust
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use std::io::BufRead;
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use std::collections::HashMap;
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#[derive(Hash, Eq, PartialEq)]
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struct Symbol(char, usize, usize);
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fn main() {
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let schematic = read_lines("input.txt");
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let mut part_sum = 0;
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let mut gear_ratio_sum: u32 = 0;
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let mut first_gears = HashMap::new(); // Symbol: first_gear
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for (n_line, line) in schematic.iter().enumerate() {
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// println!("{} {}", n_line, line);
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let mut num_begin: usize = usize::MAX;
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let mut num_end: usize = usize::MAX;
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for (n_char, c) in line.char_indices() {
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if num_begin == usize::MAX {
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if is_digit(c) { num_begin = n_char; }
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}
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else { // in number
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if !is_digit(c) {
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num_end = n_char - 1;
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}
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else if n_char == line.chars().count() - 1 { // last char
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num_end = n_char;
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}
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if num_end != usize::MAX {
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let symbol = find_symbol(&schematic, n_line, num_begin, n_char-1);
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if symbol != NO_SYMBOL {
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let num = line[num_begin..=num_end].parse::<u32>().expect("Could not parse number");
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part_sum += num;
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if symbol.0 == '*' {
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if first_gears.contains_key(&symbol) {
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gear_ratio_sum += first_gears[&symbol] * num;
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}
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else { first_gears.insert(symbol, num); }
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}
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}
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num_begin = usize::MAX;
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num_end = usize::MAX;
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}
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}
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}
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}
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println!("Total sum of part numbers: {}", part_sum);
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println!("Total sum of gear ratios: {}", gear_ratio_sum);
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}
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fn is_digit(c: char) -> bool {
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return '0' <= c && c <= '9'
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}
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fn is_symbol(c: char) -> bool {
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return c != '.' && (!is_digit(c));
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}
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const NO_SYMBOL:Symbol = Symbol('\0', usize::MAX, usize::MAX);
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// return symbol and its position
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fn find_symbol(schematic: &Vec<String>, num_line: usize, num_begin: usize, num_end: usize) -> Symbol {
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// search char left and right
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if num_begin > 0 {
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let c = schematic[num_line].chars().nth(num_begin-1).unwrap();
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if is_symbol(c) { return Symbol(c, num_line, num_begin - 1); }
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}
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if num_end + 1 < schematic[num_line].chars().count() {
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let c = schematic[num_line].chars().nth(num_end+1).unwrap();
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if is_symbol(c) { return Symbol(c, num_line, num_end + 1); }
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}
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let skip: usize = num_begin.saturating_sub(1);
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let take: usize;
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if num_begin == 0 {
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take = num_end.saturating_sub(num_begin) + 2;
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} else {
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take = num_end.saturating_sub(num_begin) + 3;
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}
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// search top line
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if num_line > 0 {
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for (i, c) in schematic[num_line-1].char_indices().skip(skip).take(take) {
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if is_symbol(c) { return Symbol(c, num_line-1, i); }
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}
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}
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// search bottom line
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if num_line + 1 < schematic.len() {
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for (i, c) in schematic[num_line+1].char_indices().skip(skip).take(take) {
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if is_symbol(c) { return Symbol(c, num_line+1, i); }
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}
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}
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return NO_SYMBOL;
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}
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fn read_lines<P>(filename: P) -> Vec<String>
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where P: AsRef<std::path::Path>, {
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return match std::fs::File::open(filename) {
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Err(why) => panic!("Could not open file. {}", why),
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Ok(file) => std::io::BufReader::new(file).lines().map(|l| {l.expect("Could not parse line")}).collect(),
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};
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}
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