95 lines
3.3 KiB
Rust
95 lines
3.3 KiB
Rust
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use std::io::{self, BufRead};
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fn get_diff_bits_count(a: u32, b: u32) -> usize { // return 0 if equal, 1 if 1 bit is different, else 2
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let diff = a ^ b;
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if diff == 0 { return 0 }
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if (diff & diff.overflowing_sub(1).0) == 0 { return 1 }
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return 2;
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}
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fn find_reflection_axis(pattern: &Vec<u32>, has_smack: bool) -> Option<usize> {
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for i in 1..pattern.len() {
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let mut found_smack = false;
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let diff = get_diff_bits_count(pattern[i-1], pattern[i]);
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if has_smack && diff == 1 {
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found_smack = true;
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}
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if diff == 0 || found_smack { // find two identical neighbors (or differing by 1 for task 2
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let mut matching = true;
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for j in 1..i.min(pattern.len() - i) { // check top and bottom if equal (or diff by 1 bit if has_smack)
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let diff = get_diff_bits_count(pattern[i-1-j], pattern[i+j]);
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if diff == 0 { continue; }
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if has_smack && diff == 1 && !found_smack { // allow only one smack
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found_smack = true;
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continue;
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}
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matching = false;
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break;
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}
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if matching && (!has_smack || (has_smack && found_smack)) { // require smack for task 2
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return Some(i);
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}
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}
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}
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return None;
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}
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fn do_task(horizontal: &Vec<u32>, vertical: &Vec<u32>, has_smack: bool) -> usize {
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let mut mirror_sum: usize = 0;
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if let Some(x) = find_reflection_axis(&horizontal, has_smack) {
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mirror_sum += x * 100;
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}
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if let Some(x) = find_reflection_axis(&vertical, has_smack) {
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mirror_sum += x;
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}
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return mirror_sum;
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}
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fn main() {
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// let input = "example.txt";
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let input = "input.txt";
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let lines = read_lines(&input);
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let mut horizontal: Vec<u32> = Vec::new();
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let mut vertical: Vec<u32> = Vec::new();
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horizontal.reserve(20);
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vertical.reserve(20);
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let mut mirror_sum1: usize = 0;
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let mut mirror_sum2: usize = 0;
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let convert = |c| -> u32 { if c == '#' { 1 } else { 0 } };
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for line in lines.map(|r| r.ok().unwrap()) {
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if line.len() == 0 {
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if horizontal.len() != 0 { // skip first time
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mirror_sum1 += do_task(&horizontal, &vertical, false);
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mirror_sum2 += do_task(&horizontal, &vertical, true);
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}
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horizontal.clear();
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vertical.clear();
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continue;
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}
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if horizontal.len() == 0 { // 0 for each column
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(0..line.len()).for_each(|_| vertical.push(0));
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}
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horizontal.push(0);
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for (i, n) in line.chars().map(|c| convert(c)).enumerate() {
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*horizontal.last_mut().unwrap() |= (n << i);
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vertical[i] |= (n << (horizontal.len()-1));
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}
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}
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mirror_sum1 += do_task(&horizontal, &vertical, false);
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mirror_sum2 += do_task(&horizontal, &vertical, true);
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println!("Sum: (1): {}", mirror_sum1);
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println!("Sum: (2): {}", mirror_sum2);
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}
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fn read_lines<P>(filename: P) -> io::Lines<io::BufReader<std::fs::File>>
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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()
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};
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}
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