Robotti

warning: comparison is useless due to type limits
  --> input/code.rs:23:12
   |
23 |         if pos.0 < 0 || pos.1 < 0 || pos.0 >= n || pos.1 >= n {
   |            ^^^^^^^^^
   |
   = note: `#[warn(unused_comparisons)]` on by default

warning: comparison is useless due to type limits
  --> input/code.rs:23:25
   |
23 |         if pos.0 < 0 || pos.1 < 0 || pos.0 >= n || pos.1 >= n {
   |                         ^^^^^^^^^

warning: 2 warnings emitted

enum Direction {
    Up,
    Down,
    Left,
    Right
}

fn main() {
    let mut input = String::new();
    std::io::stdin().read_line(&mut input).unwrap();
    let n: usize = input.trim().parse().unwrap();
    let mut grid: Vec<Vec<char>> = Vec::new();
    for _ in 0..n {
        let mut input = String::new();
        std::io::stdin().read_line(&mut input).unwrap();
        grid.push(input.chars().collect());
    }

    let mut counter = 0;
    let mut pos = (0, 0);
    let mut dir = Direction::Down;
    loop {
        if pos.0 < 0 || pos.1 < 0 || pos.0 >= n || pos.1 >= n {
            break;
        }
        counter += 1;
        match grid[pos.1][pos.0] {
            '.' => {}
            '/' => {dir = match dir {
                Direction::Up => Direction::Right,
                Direction::Down => Direction::Left,
                Direction::Left => Direction::Down,
                Direction::Right => Direction::Up,
            };
            grid[pos.1][pos.0] = '\\';
        },
            '\\' => {dir = match dir {
                Direction::Up => Direction::Left,
                Direction::Down => Direction::Right,
                Direction::Left => Direction::Up,
                Direction::Right => Direction::Down,
            };
            grid[pos.1][pos.0] = '/';
        }
            _ => panic!(),            
        }
        match dir {
            Direction::Up => pos.1 -= 1,
            Direction::Down => pos.1 += 1,
            Direction::Left => pos.0 -= 1,
            Direction::Right => pos.0 += 1,
        }
    }
    println!("{counter}");
}

Test 1 (public)

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: ACCEPTED