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use std::io::{self, Read};
struct Runs<T, I> {
inner: I,
current: Option<T>,
count: usize,
}
impl<T, I> From<I> for Runs<T, I> {
fn from(iter: I) -> Self {
Runs {
inner: iter,
current: None,
count: 0,
}
}
}
// Gross.
impl<T: Copy + PartialEq, I: Iterator<Item = T>> Iterator for Runs<T, I> {
type Item = (T, usize);
fn next(&mut self) -> Option<(T, usize)> {
for c in &mut self.inner {
match self.current {
None => {
self.current = Some(c);
self.count = 1;
},
Some(r) if r == c => {
self.count += 1;
},
Some(r) => {
self.current = Some(c);
let run = self.count;
self.count = 1;
return Some((r, run));
},
}
}
self.current.take().map(|c| (c, self.count))
}
}
fn solve(input: &str) -> String {
let len = input.find('\n').unwrap_or(input.len());
let mut columns = vec![Vec::new(); len];
for line in input.lines() {
for (i, c) in line.chars().enumerate() {
columns[i].push(c);
}
}
columns.into_iter()
.map(|mut column| {
column.sort();
Runs::from(column.into_iter())
.max_by_key(|run| run.1)
.unwrap()
.0
})
.collect()
}
fn main() {
let mut input = String::new();
io::stdin().read_to_string(&mut input).unwrap();
println!("Part 1: {}", solve(&input));
}
#[test]
fn part1() {
let input = "
eedadn
drvtee
eandsr
raavrd
atevrs
tsrnev
sdttsa
rasrtv
nssdts
ntnada
svetve
tesnvt
vntsnd
vrdear
dvrsen
enarar
";
assert_eq!("easter", solve(input.trim()));
}
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