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fn mogu_levo(c: char) -> bool {
return c == 'S' || c == 'L' || c == 'F' || c == '-';
}
fn mogu_desno(c: char) -> bool {
return c == 'S' || c == '7' || c == 'J' || c == '-';
}
fn mogu_gore(c: char) -> bool {
return c == 'S' || c == '7' || c == 'F' || c == '|';
}
fn mogu_dole(c: char) -> bool {
return c == 'S' || c == 'L' || c == 'J' || c == '|';
}
fn bfs(input: &Vec<String>, was: &mut Vec<Vec<bool>>, x: i32, y: i32, s: u32) -> u32 {
if s > 2 && input[y as usize].chars().nth(x as usize).unwrap() == 'S' {
return s;
}
if was[y as usize][x as usize] {
return 0;
}
was[y as usize][x as usize] = true;
for (dx, dy) in [(-1, 0), (1, 0), (0, -1), (0, 1)] {
let nx = x + dx;
let ny = y + dy;
if nx >= 0 && nx < input[y as usize].len() as i32 && ny >= 0 && ny < input.len() as i32 {
let t = input[y as usize].chars().nth(x as usize).unwrap();
let n = input[ny as usize].chars().nth(nx as usize).unwrap();
let ind: bool;
if dx == 1 {
ind = mogu_levo(t) && mogu_desno(n);
} else if dx == -1 {
ind = mogu_desno(t) && mogu_levo(n);
} else if dy == 1 {
ind = mogu_gore(t) && mogu_dole(n);
} else {
ind = mogu_dole(t) && mogu_gore(n);
}
if !ind {
continue;
}
let ret = bfs(input, was, nx, ny, s + 1);
// was[ny as usize][nx as usize] = false;
if ret != 0 {
return ret;
}
}
}
return 0;
}
fn set_s(input: &mut Vec<String>, xs: i32, ys: i32) {
let levi = mogu_levo(input[ys as usize].chars().nth(xs as usize - 1).unwrap());
let gornji = mogu_gore(input[ys as usize - 1].chars().nth(xs as usize).unwrap());
let donji = mogu_dole(input[ys as usize + 1].chars().nth(xs as usize).unwrap());
let desni = mogu_desno(input[ys as usize].chars().nth(xs as usize + 1).unwrap());
if donji && gornji {
input[ys as usize] = input[ys as usize].replace("S", "|");
} else if donji && levi {
input[ys as usize] = input[ys as usize].replace("S", "7");
} else if donji && desni {
input[ys as usize] = input[ys as usize].replace("S", "F");
} else if gornji && levi {
input[ys as usize] = input[ys as usize].replace("S", "J");
} else if gornji && desni {
input[ys as usize] = input[ys as usize].replace("S", "L");
} else if levi && desni {
input[ys as usize] = input[ys as usize].replace("S", "-");
} else {
panic!();
}
}
fn part2(input: &Vec<String>, was: Vec<Vec<bool>>) -> u32 {
let mut s: u32 = 0;
let mut en: bool;
let mut lc: char;
for i in 0..input.len() {
en = false;
lc = 'S';
for j in 0..input[i].len() {
let c = input[i].chars().nth(j).unwrap();
if !was[i][j] {
s += en as u32;
continue;
}
if c == '-' {
continue;
} else if c == '|' {
en = !en;
continue;
}
if lc == 'S' {
lc = c;
if lc == 'J' || lc == '7' {
panic!();
}
} else {
if (lc == 'F' && c == 'J') || (lc == 'L' && c == '7') {
en = !en;
}
lc = 'S';
}
}
}
return s;
}
pub fn main() {
let txt = std::fs::read_to_string("./input/day10.txt").unwrap();
let mut input: Vec<_> = vec![];
for line in txt.lines() {
input.push(line.to_string());
}
let mut xs = 0;
let mut ys = 0;
for i in 0..input.len() {
for j in 0..input[i].len() {
if input[i].chars().nth(j).unwrap() == 'S' {
xs = j as i32;
ys = i as i32;
}
}
}
let mut was = vec![vec![false; input[0].len()]; input.len()];
bfs(&input, &mut was, xs, ys, 0);
set_s(&mut input, xs, ys);
println!("{}", part2(&input, was));
}
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