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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,78 @@ | ||
use itertools::izip; | ||
|
||
pub fn part1(data: &str) -> usize { | ||
let lines = data.lines().collect::<Vec<_>>(); | ||
let mut result = 0; | ||
for (y, line) in lines.iter().enumerate() { | ||
for x in 0..line.len() { | ||
for dy in -1..=1 { | ||
for dx in -1..=1 { | ||
if "XMAS".bytes().enumerate().all(|(i, b)| { | ||
y.checked_add_signed(i as isize * dy) | ||
.and_then(|y| lines.get(y)) | ||
.and_then(|line| { | ||
x.checked_add_signed(i as isize * dx) | ||
.and_then(|x| line.as_bytes().get(x)) | ||
}) | ||
== Some(&b) | ||
}) { | ||
result += 1; | ||
} | ||
} | ||
} | ||
} | ||
} | ||
result | ||
} | ||
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pub fn part2(data: &str) -> usize { | ||
let lines = data.lines().collect::<Vec<_>>(); | ||
let mut result = 0; | ||
for (above, line, below) in izip!(&lines[..], &lines[1..], &lines[2..]) { | ||
for (nw, ne, b, sw, se) in izip!( | ||
above.bytes(), | ||
above.bytes().skip(2), | ||
line.bytes().skip(1), | ||
below.bytes(), | ||
below.bytes().skip(2) | ||
) { | ||
if b == b'A' | ||
&& (nw == b'M' && se == b'S' || se == b'M' && nw == b'S') | ||
&& (ne == b'M' && sw == b'S' || sw == b'M' && ne == b'S') | ||
{ | ||
result += 1; | ||
} | ||
} | ||
} | ||
result | ||
} | ||
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#[cfg(test)] | ||
mod tests { | ||
use super::*; | ||
use indoc::indoc; | ||
use pretty_assertions::assert_eq; | ||
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static EXAMPLE: &str = indoc! {" | ||
MMMSXXMASM | ||
MSAMXMSMSA | ||
AMXSXMAAMM | ||
MSAMASMSMX | ||
XMASAMXAMM | ||
XXAMMXXAMA | ||
SMSMSASXSS | ||
SAXAMASAAA | ||
MAMMMXMMMM | ||
MXMXAXMASX | ||
"}; | ||
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#[test] | ||
fn part1_examples() { | ||
assert_eq!(18, part1(EXAMPLE)); | ||
} | ||
|
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#[test] | ||
fn part2_examples() { | ||
assert_eq!(9, part2(EXAMPLE)); | ||
} | ||
} |
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Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -1,3 +1,4 @@ | ||
pub mod day1; | ||
pub mod day2; | ||
pub mod day3; | ||
pub mod day4; |
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