72 lines
1.6 KiB
Rust
72 lines
1.6 KiB
Rust
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use std::fs;
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use itertools::Itertools;
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fn main() -> Result<(), Box<dyn std::error::Error>> {
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let input = fs::read_to_string("input")?;
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let input = parse_number_list(input)?;
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let numbers = find_2020_numbers(input, 3)?;
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println!("{}", numbers.iter().product::<u32>());
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Ok(())
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}
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fn parse_number_list(input: String) -> Result<Vec<u32>, std::num::ParseIntError> {
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input.lines().map(|line| line.parse::<u32>()).collect()
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}
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fn find_2020_numbers(input: Vec<u32>, sum_number: usize) -> Result<Vec<u32>, String> {
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input
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.into_iter()
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.combinations(sum_number)
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.find(|i| i.iter().sum::<u32>() == 2020)
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.ok_or("Could not find 2020.".to_string())
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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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use indoc::indoc;
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#[test]
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fn test_first_example() -> Result<(), Box<dyn std::error::Error>> {
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let example = indoc!(
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"
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1721
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979
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366
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299
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675
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1456
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"
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);
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let example = parse_number_list(example.to_string())?;
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let numbers = find_2020_numbers(example, 2)?;
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assert_eq!(numbers.iter().product::<u32>(), 514579);
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Ok(())
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}
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#[test]
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fn test_second_example() -> Result<(), Box<dyn std::error::Error>> {
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let example = indoc!(
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"
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1721
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979
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366
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299
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675
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1456
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"
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);
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let example = parse_number_list(example.to_string())?;
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let numbers = find_2020_numbers(example, 3)?;
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assert_eq!(numbers.iter().to_owned().product::<u32>(), 241861950);
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Ok(())
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}
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}
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