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@@ -0,0 +1,249 @@
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+use std::error::Error;
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+use std::fmt;
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+use std::fs;
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+use std::result;
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+
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+type Result<T> = result::Result<T, Box<Error>>;
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+
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+const INPUT: &str = "inputs/14.txt";
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+
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+#[derive(Debug, PartialEq)]
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+struct Recipes {
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+ scores: Vec<u8>,
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+ elf1_index: usize,
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+ elf2_index: usize,
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+}
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+
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+impl fmt::Display for Recipes {
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+ #[allow(clippy::write_with_newline)]
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+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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+ for (index, score) in self.scores.iter().enumerate() {
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+ if index == self.elf1_index {
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+ write!(f, "({})", score)?;
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+ } else if index == self.elf2_index {
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+ write!(f, "[{}]", score)?;
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+ } else {
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+ write!(f, " {} ", score)?;
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+ }
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+ }
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+ write!(f, "\n")?;
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+ Ok(())
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+ }
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+}
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+
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+impl Recipes {
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+ fn new() -> Recipes {
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+ Recipes {
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+ scores: vec![3, 7],
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+ elf1_index: 0,
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+ elf2_index: 1,
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+ }
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+ }
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+
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+ fn new_recipes(&mut self) {
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+ let elf1_score = self.scores[self.elf1_index];
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+ let elf2_score = self.scores[self.elf2_index];
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+ let sum = elf1_score + elf2_score;
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+ fn push_digits(n: u8, digits: &mut Vec<u8>) {
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+ if n >= 10 {
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+ push_digits(n / 10, digits);
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+ }
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+ digits.push(n % 10);
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+ }
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+ push_digits(sum, &mut self.scores);
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+ }
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+
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+ fn pick_recipes(&mut self) {
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+ let elf1_score = self.scores[self.elf1_index];
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+ let elf2_score = self.scores[self.elf2_index];
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+ self.elf1_index = (self.elf1_index + (1 + elf1_score as usize)) % self.scores.len();
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+ self.elf2_index = (self.elf2_index + (1 + elf2_score as usize)) % self.scores.len();
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+ }
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+
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+ fn scores_after_n_recipes(&mut self, n: usize, num_scores: usize) -> String {
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+ while self.scores.len() < n + num_scores {
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+ self.new_recipes();
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+ self.pick_recipes();
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+ }
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+ self.scores[n..n + num_scores].iter().map(|score| format!("{}", score)).collect()
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+ }
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+
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+ fn find_index_of_sequence(&mut self, seq: &[u8]) -> usize {
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+ let seq_len = seq.len();
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+ loop {
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+ let scores_len = self.scores.len();
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+ self.new_recipes();
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+ self.pick_recipes();
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+ let new_scores_len = self.scores.len();
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+ let diff = new_scores_len - scores_len;
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+ if scores_len >= seq_len {
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+ for i in 0..diff {
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+ let seq_index = scores_len + i - seq_len;
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+ if &self.scores[seq_index..(seq_index + seq_len)] == seq {
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+ return seq_index;
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+ }
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+ }
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+ }
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+ }
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+ }
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+}
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+
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+fn digit_seq(n: &str) -> Vec<u8> {
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+ let mut digits: Vec<u8> = vec![];
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+ for digit in n.chars() {
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+ digits.push(digit.to_digit(10).unwrap() as u8);
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+ }
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+ digits
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+}
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+
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+fn read_input_file(filename: &str) -> Result<usize> {
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+ let input = fs::read_to_string(filename)?;
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+ Ok(input.trim().parse()?)
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+}
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+
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+pub fn solve_part1() -> Result<String> {
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+ let input = read_input_file(INPUT)?;
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+ let mut recipes = Recipes::new();
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+ Ok(recipes.scores_after_n_recipes(input, 10))
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+}
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+
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+pub fn solve_part2() -> Result<usize> {
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+ let input = fs::read_to_string(INPUT)?;
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+ let mut recipes = Recipes::new();
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+ let seq = digit_seq(&input.trim());
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+ Ok(recipes.find_index_of_sequence(&seq[..]))
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+}
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+
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+#[cfg(test)]
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+mod tests {
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+ use super::*;
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+
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+ #[test]
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+ fn creates_new_recipes_struct() {
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+ let recipes = Recipes::new();
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+ assert_eq!(recipes.scores, vec![3, 7]);
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+ assert_eq!(recipes.elf1_index, 0);
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+ assert_eq!(recipes.elf2_index, 1);
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+ }
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+
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+ #[test]
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+ fn adds_new_recipes() {
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+ let mut recipes = Recipes::new();
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+ recipes.new_recipes();
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+ assert_eq!(recipes.scores, vec![3, 7, 1, 0]);
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+ }
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+
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+ #[test]
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+ fn picks_new_recipes() {
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+ let mut recipes = Recipes::new();
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+ recipes.new_recipes();
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+ recipes.pick_recipes();
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+ assert_eq!(recipes.elf1_index, 0);
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+ assert_eq!(recipes.elf2_index, 1);
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+ }
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+
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+ #[test]
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+ fn iterates_15_times() {
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+ let mut recipes = Recipes::new();
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+ for _ in 0..15 {
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+ recipes.new_recipes();
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+ recipes.pick_recipes();
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+ }
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+ assert_eq!(
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+ format!("{}", recipes),
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+ " 3 7 1 0 [1] 0 1 2 (4) 5 1 5 8 9 1 6 7 7 9 2 \n",
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+ );
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+ }
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+
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+ #[test]
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+ fn scores_after_5_recipes() {
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+ let mut recipes = Recipes::new();
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+ assert_eq!(
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+ recipes.scores_after_n_recipes(5, 10),
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+ "0124515891",
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+ );
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+ }
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+
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+ #[test]
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+ fn scores_after_9_recipes() {
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+ let mut recipes = Recipes::new();
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+ assert_eq!(
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+ recipes.scores_after_n_recipes(9, 10),
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+ "5158916779",
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+ );
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+ }
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+
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+ #[test]
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+ fn scores_after_18_recipes() {
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+ let mut recipes = Recipes::new();
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+ assert_eq!(
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+ recipes.scores_after_n_recipes(18, 10),
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+ "9251071085",
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+ );
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+ }
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+
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+ #[test]
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+ fn scores_after_2018_recipes() {
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+ let mut recipes = Recipes::new();
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+ assert_eq!(
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+ recipes.scores_after_n_recipes(2018, 10),
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+ "5941429882",
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+ );
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+ }
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+
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+ #[test]
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+ fn finds_index_of_sequence_1() {
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+ let mut recipes = Recipes::new();
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+ let seq = vec![5, 1, 5, 8, 9];
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+ assert_eq!(
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+ recipes.find_index_of_sequence(&seq[..]),
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+ 9,
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+ );
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+ }
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+
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+ #[test]
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+ fn finds_index_of_sequence_2() {
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+ let mut recipes = Recipes::new();
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+ let seq = vec![0, 1, 2, 4, 5];
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+ assert_eq!(
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+ recipes.find_index_of_sequence(&seq[..]),
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+ 5,
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+ );
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+ }
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+
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+ #[test]
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+ fn finds_index_of_sequence_3() {
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+ let mut recipes = Recipes::new();
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+ let seq = vec![9, 2, 5, 1, 0];
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+ assert_eq!(
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+ recipes.find_index_of_sequence(&seq[..]),
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+ 18,
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+ );
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+ }
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+
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+ #[test]
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+ fn finds_index_of_sequence_4() {
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+ let mut recipes = Recipes::new();
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+ let seq = vec![5, 9, 4, 1, 4];
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+ assert_eq!(
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+ recipes.find_index_of_sequence(&seq[..]),
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+ 2018,
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+ );
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+ }
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+
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+ #[test]
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+ fn gets_digit_seq_1() {
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+ assert_eq!(
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+ digit_seq("51589"),
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+ vec![5, 1, 5, 8, 9],
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+ );
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+ }
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+
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+ #[test]
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+ fn gets_digit_seq_2() {
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+ assert_eq!(
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+ digit_seq("01245"),
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+ vec![0, 1, 2, 4, 5],
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+ );
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+ }
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+}
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