Improved Day 8 Part 2
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3a8ea28480
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249
src/main.rs
249
src/main.rs
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@ -1,6 +1,4 @@
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#![feature(test)]
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use std::collections::HashMap;
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extern crate test;
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const INPUTS: [&'static str; 2] = [
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@ -12,215 +10,86 @@ const fn map_to_segment(c: char) -> u8 {
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1 << (c as u8 - b'a')
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}
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fn parse_digits(ip: &str) -> Vec<u8> {
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let mut out = Vec::with_capacity(ip.len());
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fn parse_input(input: &'static str) -> impl Iterator<Item = (Vec<u8>, Vec<u8>)> {
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input.lines().filter(|&x| !x.is_empty()).map(|line| {
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let (hints, displays) = line.split_once(" | ").unwrap();
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for c in ip.chars() {
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out.push(map_to_segment(c));
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}
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out.sort_unstable();
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out
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}
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fn parse_input(input: &'static str) -> Vec<(Vec<Vec<u8>>, Vec<Vec<u8>>)> {
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input
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.lines()
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.filter(|&x| !x.is_empty())
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.map(|line| {
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let (hints, displays) = line.split_once(" | ").unwrap();
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let hints = hints
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.split(' ')
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.filter(|x| !x.is_empty())
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.map(parse_digits)
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.collect();
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let digits = displays
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.split(' ')
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.filter(|x| !x.is_empty())
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.map(parse_digits)
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.collect();
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(hints, digits)
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})
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.collect()
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}
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pub fn permute(mut nums: [u8; 7]) -> Vec<[u8; 7]> {
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let mut ans = vec![];
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let k = nums.len();
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permute_helper(&mut nums, &mut ans, k);
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ans
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}
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fn permute_helper(nums: &mut [u8; 7], permutations: &mut Vec<[u8; 7]>, k: usize) {
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if k == 1 {
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permutations.push(*nums);
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} else {
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for i in 0..k {
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permute_helper(nums, permutations, k - 1);
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if i < k - 1 {
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if k % 2 == 0 {
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nums.swap(i, k - 1);
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} else {
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nums.swap(0, k - 1);
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let hints = hints
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.split(' ')
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.filter(|x| !x.is_empty())
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.map(|hint| {
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let mut out = 0;
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for c in hint.chars() {
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out |= map_to_segment(c);
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}
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}
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}
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}
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out
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})
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.collect();
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let digits = displays
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.split(' ')
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.filter(|x| !x.is_empty())
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.map(|hint| {
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let mut out = 0;
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for c in hint.chars() {
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out |= map_to_segment(c);
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}
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out
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})
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.collect();
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(hints, digits)
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})
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}
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fn generate_charset(permutation: &[u8]) -> Vec<Vec<u8>> {
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let mut answer = vec![vec![]; 10];
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fn decode_hint(hints: Vec<u8>) -> [u8; 10] {
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let mut out = [0; 10];
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for digit in 0..=9 {
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let mut out = vec![];
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for &hint in hints.iter() {
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match hint.count_ones() {
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2 => out[1] = hint,
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4 => out[4] = hint,
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3 => out[7] = hint,
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7 => out[8] = hint,
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match digit {
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0 => {
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out.push(permutation[0]);
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out.push(permutation[1]);
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out.push(permutation[2]);
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out.push(permutation[4]);
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out.push(permutation[5]);
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out.push(permutation[6]);
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}
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1 => {
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out.push(permutation[2]);
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out.push(permutation[5]);
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}
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2 => {
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out.push(permutation[0]);
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out.push(permutation[2]);
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out.push(permutation[3]);
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out.push(permutation[4]);
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out.push(permutation[6]);
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}
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3 => {
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out.push(permutation[0]);
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out.push(permutation[2]);
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out.push(permutation[3]);
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out.push(permutation[5]);
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out.push(permutation[6]);
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}
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4 => {
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out.push(permutation[1]);
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out.push(permutation[2]);
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out.push(permutation[3]);
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out.push(permutation[5]);
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}
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5 => {
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out.push(permutation[0]);
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out.push(permutation[1]);
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out.push(permutation[3]);
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out.push(permutation[5]);
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out.push(permutation[6]);
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}
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6 => {
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out.push(permutation[0]);
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out.push(permutation[1]);
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out.push(permutation[3]);
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out.push(permutation[4]);
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out.push(permutation[5]);
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out.push(permutation[6]);
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}
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7 => {
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out.push(permutation[0]);
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out.push(permutation[2]);
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out.push(permutation[5]);
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}
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8 => {
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out.push(permutation[0]);
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out.push(permutation[1]);
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out.push(permutation[2]);
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out.push(permutation[3]);
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out.push(permutation[4]);
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out.push(permutation[5]);
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out.push(permutation[6]);
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}
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9 => {
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out.push(permutation[0]);
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out.push(permutation[1]);
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out.push(permutation[2]);
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out.push(permutation[3]);
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out.push(permutation[5]);
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out.push(permutation[6]);
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}
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_ => (),
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}
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answer[digit] = out;
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}
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answer
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.into_iter()
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.map(|mut set| {
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set.sort_unstable();
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set
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})
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.collect()
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}
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for hint in hints {
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let one_overlap = (hint & out[1]).count_ones();
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let four_overlap = (hint & out[4]).count_ones();
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#[inline]
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fn verify_perfect_overlap(d1: &[u8], d2: &[u8]) -> bool {
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if d1.len() != d2.len() {
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return false;
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}
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d1 == d2
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}
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fn find_best_fit(permutations: &[[u8; 7]], mut hints: Vec<Vec<u8>>) -> Option<Vec<Vec<u8>>> {
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hints.sort_unstable_by(|a, b| a.len().cmp(&b.len()));
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for permutation in permutations {
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let charset = generate_charset(permutation);
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let mut map = HashMap::new();
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for (i, cset) in charset.iter().enumerate() {
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for hint in hints.iter() {
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if verify_perfect_overlap(&cset, &hint) {
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if map.contains_key(&hint) {
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continue;
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} else {
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map.insert(hint, i);
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}
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}
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}
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}
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if map.len() == hints.len() {
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return Some(charset);
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match (hint.count_ones(), one_overlap, four_overlap) {
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(5, 1, 2) => out[2] = hint,
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(5, 2, 3) => out[3] = hint,
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(5, 1, 3) => out[5] = hint,
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(6, 1, 3) => out[6] = hint,
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(6, 2, 4) => out[9] = hint,
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(6, 2, 3) => out[0] = hint,
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_ => (),
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}
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}
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None
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return out;
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}
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fn solution(input: Vec<(Vec<Vec<u8>>, Vec<Vec<u8>>)>) -> u64 {
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// Generate all possible permutations of abcdefg
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let permutations = permute([
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0b0000001, 0b0000010, 0b0000100, 0b0001000, 0b0010000, 0b0100000, 0b1000000,
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]);
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fn solution(input: impl Iterator<Item = (Vec<u8>, Vec<u8>)>) -> i32 {
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let mut answer = 0;
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for (hints, digits) in input {
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let best_fit = find_best_fit(&permutations, hints).unwrap();
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let decoded_hints = decode_hint(hints);
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let mut out = 0;
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let mut out_digit = String::new();
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for digit in digits {
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for (i, fit) in best_fit.iter().enumerate() {
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if fit == &digit {
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out_digit.push_str(&i.to_string());
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let offset = digits.len() as u32;
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for (j, digit) in digits.into_iter().enumerate() {
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for (i, &hint) in decoded_hints.iter().enumerate() {
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if hint == digit {
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out += i as i32 * 10i32.pow(offset - j as u32 - 1);
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}
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}
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}
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let parsed = u64::from_str_radix(&out_digit, 10).unwrap();
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answer += parsed;
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answer += out;
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}
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answer
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@ -236,9 +105,9 @@ fn main() {
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#[bench]
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fn solution_bench(b: &mut test::Bencher) {
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let input = parse_input(INPUTS[1]);
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b.iter(|| {
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let result = solution(input.clone());
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let input = parse_input(INPUTS[1]);
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let result = solution(input);
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test::black_box(result);
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})
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}
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