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use advent_lib::prelude::*;
fn main() -> Result<()> {
let mut args = std::env::args();
if args.len() != 2 {
eprintln!("Usage: advent input");
}
let _ = args.next();
let filename = args.next().unwrap();
let input = advent_lib::read_lines_file(&filename)?;
let mut value_grid = Vec::new();
let mut risk_grid: Vec<Vec<Option<i64>>> = Vec::new();
for line in &input{
let mut value_row = Vec::new();
let mut risk_row = Vec::new();
for c in line.chars() {
let value = c.to_digit(10).unwrap() as i64;
value_row.push(value);
risk_row.push(None);
}
value_grid.push(value_row);
risk_grid.push(risk_row);
}
let height = value_grid.len();
let width = value_grid[0].len();
/*
risk_grid[0][0] = Some(0);
find_path(0, 0, &value_grid, &mut risk_grid, false);
let risk = risk_grid[height - 1][width - 1].unwrap();
println!("{}", risk);
*/
let mut big_risk_grid = Vec::new();
for _ in 0 .. height * 5 {
let mut big_risk_grid_row = Vec::new();
for _ in 0 .. width * 5 {
big_risk_grid_row.push(None);
}
big_risk_grid.push(big_risk_grid_row);
}
big_risk_grid[0][0] = Some(0);
find_path(0, 0, &value_grid, &mut big_risk_grid, true);
let big_risk = big_risk_grid[height * 5 - 1][width * 5 - 1].unwrap();
println!("{}", big_risk);
Ok(())
}
#[allow(dead_code)]
fn debug_risk_grid(risk_grid: &Vec<Vec<Option<i64>>>) {
for row in risk_grid {
for cell in row {
match cell {
None => { print!(" ."); }
Some(n) => { print!(" {}", n); }
}
}
println!("");
}
println!("");
}
fn find_path(x: usize, y: usize, value_grid: &Vec<Vec<i64>>,
risk_grid: &mut Vec<Vec<Option<i64>>>, repeat: bool)
{
let mut height = value_grid.len();
let mut width = value_grid[0].len();
if repeat {
width *= 5;
height *= 5;
}
let mut exploration_stack = Vec::new();
exploration_stack.push((x, y));
let mut counter = 0;
loop {
let (x, y) = match exploration_stack.pop() {
None => { return; }
Some(value) => { value }
};
let risk_so_far = risk_grid[y][x].unwrap();
counter += 1;
if counter % 100000 == 0 {
print!(" [{},{} {}]", x, y, risk_so_far);
}
if x > 0 {
let value_left = get_value(x - 1, y, value_grid);
let new_risk_left = risk_so_far + value_left;
let risk_left = risk_grid[y][x-1];
let should_move = match risk_left {
None => true,
Some(prior_best_risk) => {
new_risk_left < prior_best_risk
}
};
if should_move {
risk_grid[y][x-1] = Some(new_risk_left);
exploration_stack.push((x - 1, y));
}
}
if y > 0 {
let value_up = get_value(x, y - 1, value_grid);
let new_risk_up = risk_so_far + value_up;
let risk_up = risk_grid[y-1][x];
let should_move = match risk_up {
None => true,
Some(prior_best_risk) => {
new_risk_up < prior_best_risk
}
};
if should_move {
risk_grid[y-1][x] = Some(new_risk_up);
exploration_stack.push((x, y - 1));
}
}
if x + 1 < width {
let value_right = get_value(x + 1, y, value_grid);
let new_risk_right = risk_so_far + value_right;
let risk_right = risk_grid[y][x+1];
let should_move = match risk_right {
None => true,
Some(prior_best_risk) => {
new_risk_right < prior_best_risk
}
};
if should_move {
risk_grid[y][x+1] = Some(new_risk_right);
exploration_stack.push((x + 1, y));
}
}
if y + 1 < height {
let value_down = get_value(x, y + 1, value_grid);
let new_risk_down = risk_so_far + value_down;
let risk_down = risk_grid[y+1][x];
let should_move = match risk_down {
None => true,
Some(prior_best_risk) => {
new_risk_down < prior_best_risk
}
};
if should_move {
risk_grid[y+1][x] = Some(new_risk_down);
exploration_stack.push((x, y + 1));
}
}
}
}
fn get_value(x: usize, y: usize, value_grid: &Vec<Vec<i64>>) -> i64 {
let height = value_grid.len();
let width = value_grid[0].len();
let tile_x = x / width;
let tile_y = y / height;
let increment: i64 = (tile_x + tile_y) as i64;
let raw_value = value_grid[y % height][x % width];
(raw_value + increment - 1) % 9 + 1
}
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