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use std::fs;
use std::collections::{HashSet, VecDeque};
#[derive(Clone, Debug)]
struct Node {
goal: bool,
//size: usize,
used: usize,
avail: usize,
}
fn parse(lines: Vec<&str>) -> Vec<Vec<Node>> {
let mut nodes = Vec::with_capacity(36);
let mut y = 0;
let mut column = Vec::with_capacity(25);
// Skip the first two lines; see `input.txt' to see why
for i in 2..lines.len() {
let words: Vec<&str> = lines[i].split_ascii_whitespace().collect();
// Read the `df -h' data, ignoring the node name
let node = Node {
goal: false,
//size: words[1].trim_end_matches('T').parse().unwrap(),
used: words[2].trim_end_matches('T').parse().unwrap(),
avail: words[3].trim_end_matches('T').parse().unwrap(),
};
column.push(node);
y += 1;
// The grid size is hardcoded at 25 rows here
if y > 24 {
nodes.push(column);
y = 0;
column = Vec::with_capacity(25);
}
}
// In part 2, we want the data in the top-right corner
nodes.last_mut().unwrap()[0].goal = true;
nodes
}
fn solve_part1(state: &Vec<Vec<Node>>) -> usize {
let mut pairs = Vec::new();
for x1 in 0..state.len() {
for y1 in 0..state[0].len() {
for x2 in 0..state.len() {
for y2 in 0..state[0].len() {
// Check for a "viable pair" according to puzzle description
if (x1 != x2 || y1 != y2) && state[x1][y1].used > 0 {
if state[x1][y1].used < state[x2][y2].avail {
pairs.push(((x1, y1), (x2, y2)));
}
}
}
}
}
}
pairs.len()
}
fn serialize(state: &Vec<Vec<Node>>) -> String {
let mut result = String::new();
// Print grid like the example in part 2's description.
// Some information is deliberately lost in this step.
for y in 0..state[0].len() {
for x in 0..state.len() {
if state[x][y].goal {
result.push('G');
} else if state[x][y].used > 100 {
result.push('#');
} else if state[x][y].used == 0 {
result.push('_');
} else {
result.push('.');
}
}
result.push('\n');
}
result
}
fn solve_part2(start: &Vec<Vec<Node>>) -> usize {
// We will do a breadth-first search of the state space, with the catch
// that `serialize()' maps several states onto the same representation
let mut visited = HashSet::from([serialize(&start)]);
let mut queue = VecDeque::from([(start.clone(), 0)]);
loop {
let (state, depth) = queue.pop_front().unwrap();
// End condition: did we move the target data to top-left node?
if state[0][0].goal {
return depth;
}
// There is one empty node; find its coordinates
let mut empty = (36, 25);
for x in 0..state.len() {
for y in 0..state[0].len() {
if state[x][y].used == 0 {
empty = (x, y);
}
}
}
// Get coordinates of up to four neighbours of `empty'
let mut neighbours = Vec::new();
if empty.0 > 0 {
neighbours.push((empty.0 - 1, empty.1));
}
if empty.0 < state.len() - 1 {
neighbours.push((empty.0 + 1, empty.1));
}
if empty.1 > 0 {
neighbours.push((empty.0, empty.1 - 1));
}
if empty.1 < state[0].len() - 1 {
neighbours.push((empty.0, empty.1 + 1));
}
// Generate new states, one for swapping `empty' with each neighbour
let mut new_states = Vec::new();
for neigh in neighbours {
// Some nodes are large and full; their data won't fit in `empty',
// so we ignore them. Otherwise, we assume that the data will fit;
// this assumption is justified by the example given for part 2.
if state[neigh.0][neigh.1].used > 100 {
continue;
}
let mut ns = state.clone();
let amount = ns[neigh.0][neigh.1].used;
ns[neigh.0][neigh.1].used -= amount;
ns[neigh.0][neigh.1].avail += amount;
ns[empty.0][empty.1].used += amount;
ns[empty.0][empty.1].avail -= amount;
if ns[neigh.0][neigh.1].goal {
ns[empty.0][empty.1].goal = true;
ns[neigh.0][neigh.1].goal = false;
}
new_states.push(ns);
}
for ns in new_states {
// Via `serialize()' many uninteresting states are discarded here
let ser = serialize(&ns);
if !visited.contains(&ser) {
visited.insert(ser);
queue.push_back((ns, depth + 1));
}
}
}
}
fn main() {
// Read data from input text file
let input = fs::read_to_string("input.txt").unwrap();
let lines = input.lines().collect();
let nodes = parse(lines);
// Part 1 gives 864 for me
println!("Part 1 solution: {}", solve_part1(&nodes));
// Part 2 gives 244 for me
println!("Part 2 solution: {}", solve_part2(&nodes));
}
// Disabled because I'm too lazy to rewrite `parse()'
// to make it handle different grid sizes properly
/*#[cfg(test)]
mod tests {
use super::*;
#[test]
fn part2_example1() {
let lines = vec![
"root@ebhq-gridcenter# df -h",
"Filesystem Size Used Avail Use%",
"/dev/grid/node-x0-y0 10T 8T 2T 80%",
"/dev/grid/node-x0-y1 11T 6T 5T 54%",
"/dev/grid/node-x0-y2 32T 28T 4T 87%",
"/dev/grid/node-x1-y0 9T 7T 2T 77%",
"/dev/grid/node-x1-y1 8T 0T 8T 0%",
"/dev/grid/node-x1-y2 11T 7T 4T 63%",
"/dev/grid/node-x2-y0 10T 6T 4T 60%",
"/dev/grid/node-x2-y1 9T 8T 1T 88%",
"/dev/grid/node-x2-y2 9T 6T 3T 66%",
];
let nodes = parse(lines);
assert_eq!(solve_part2(&nodes), 7);
}
}*/
|
