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use std::io::BufReader;
use std::io::prelude::*;
use std::fs::File;
fn main() {
let lines = read_file();
let mut current = 5;
for line in lines {
current = line.chars().fold(current, |current, dir| move_char_hex(current, dir));
println!("{:X}", current);
}
}
fn read_file() -> Vec<String> {
let file = BufReader::new(File::open("input.txt").unwrap());
file.lines()
.map(|line| line.unwrap().trim().to_string())
.filter(|line| line.len() > 0)
.collect()
}
//assume current in 1-9 range, and char is in UDLR
fn move_char(current: i32, dir: char) -> i32 {
match dir {
'U' => if current <= 3 { current } else { current - 3},
'D' => if current >= 7 { current } else { current + 3},
'L' => if current%3 == 1 { current } else { current - 1},
'R' => if current%3 == 0 { current } else { current + 1},
_ => panic!("Bad direction character")
}
}
// 1
// 2 3 4
// 5 6 7 8 9
// A B C
// D
fn move_char_hex(current: i32, dir: char) -> i32 {
match dir {
'U' => match current {
1|2|4|5|9 => current,
3|13 => current - 2,
_ => current - 4
},
'D' => match current {
5|10|13|12|9 => current,
1|11 => current + 1,
_ => current + 4
},
'L' => match current {
1|2|5|10|13 => current,
_ => current - 1
},
'R' => match current {
1|4|9|12|13 => current,
_ => current + 1
},
_ => panic!("Bad direction character")
}
}
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