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use std::collections::HashMap;
use std::fs;
fn solve_puzzle(lines: &Vec<&str>, use_max: bool) -> String {
let mut freqs = Vec::new();
for _i in 0..lines[0].len() {
let hm: HashMap<char, usize> = HashMap::new();
freqs.push(hm);
}
// Count char occurrences at each index in line
for line in lines {
for (i, c) in line.chars().enumerate() {
*freqs[i].entry(c).or_insert(0) += 1;
}
}
let mut result = String::new();
for hm in freqs {
let c = if use_max {
// Part 1: take most common character
hm.into_iter().max_by_key(|x| x.1).unwrap().0
} else {
// Part 2: take least common character
hm.into_iter().min_by_key(|x| x.1).unwrap().0
};
result.push(c);
}
result
}
fn main() {
// Read messages from input text file
let input = fs::read_to_string("input.txt").unwrap();
let lines = input.lines().collect();
// Part 1 gives "mlncjgdg" for me
println!("Part 1 solution: {}", solve_puzzle(&lines, true));
// Part 2 gives "bipjaytb" for me
println!("Part 2 solution: {}", solve_puzzle(&lines, false));
}
#[cfg(test)]
mod tests {
use super::*;
const EXAMPLE1_LINES: [&str; 16] = [
"eedadn", "drvtee", "eandsr", "raavrd", "atevrs", "tsrnev", "sdttsa", "rasrtv",
"nssdts", "ntnada", "svetve", "tesnvt", "vntsnd", "vrdear", "dvrsen", "enarar",
];
#[test]
fn part1_example1() {
assert_eq!(solve_puzzle(&Vec::from(EXAMPLE1_LINES), true), "easter");
}
#[test]
fn part2_example1() {
assert_eq!(solve_puzzle(&Vec::from(EXAMPLE1_LINES), false), "advent");
}
}
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