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fifteen.rs
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fifteen.rs
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use libaoc::{Day, DayNumber};
use petgraph::{algo::dijkstra, prelude::NodeIndex, Directed, Graph};
fn shortest_path(input: &[Vec<usize>]) -> usize {
let mut graph = Graph::<usize, usize, Directed>::new();
let height = input.len();
let width = input[0].len();
let nodes: Vec<NodeIndex> = input
.iter()
.flatten()
.map(|risk_level| graph.add_node(*risk_level))
.collect();
for i in 0..height {
for j in 0..width {
let node_index = nodes[i * width + j];
if j > 0 {
let neighbor_index = nodes[i * width + j - 1];
graph.add_edge(
node_index,
neighbor_index,
*graph.node_weight(neighbor_index).unwrap(),
);
}
if j < width - 1 {
let neighbor_index = nodes[i * width + j + 1];
graph.add_edge(
node_index,
neighbor_index,
*graph.node_weight(neighbor_index).unwrap(),
);
}
if i > 0 {
let neighbor_index = nodes[(i - 1) * width + j];
graph.add_edge(
node_index,
neighbor_index,
*graph.node_weight(neighbor_index).unwrap(),
);
}
if i < height - 1 {
let neighbor_index = nodes[(i + 1) * width + j];
graph.add_edge(
node_index,
neighbor_index,
*graph.node_weight(neighbor_index).unwrap(),
);
}
}
}
let map = dijkstra(&graph, nodes[0], Some(nodes[nodes.len() - 1]), |e| {
*e.weight()
});
*map.get(&nodes[nodes.len() - 1]).unwrap()
}
fn stitch_map(map: &[Vec<usize>]) -> Vec<Vec<usize>> {
let height = map.len();
let mut map_col_5: Vec<Vec<usize>> = map.to_vec();
for i in 0..height {
for j in 1..5 {
map_col_5[i].append(
&mut map[i]
.iter()
.map(|risk_level| {
if *risk_level + j >= 10 {
(*risk_level + j) % 10 + 1
} else {
*risk_level + j
}
})
.collect::<Vec<usize>>(),
);
}
}
let mut map_row_col_5 = map_col_5.clone();
for j in 1..5 {
map_row_col_5.append(
&mut map_col_5
.iter()
.map(|line| {
line.iter()
.map(|risk_level| {
if *risk_level + j >= 10 {
(*risk_level + j) % 10 + 1
} else {
*risk_level + j
}
})
.collect()
})
.collect(),
)
}
map_row_col_5
}
pub fn fifteen() -> Day<2021> {
Day::new(
DayNumber::Fifteen,
|input| {
let map: Vec<Vec<usize>> = input
.lines()
.map(|line| {
line.bytes()
.map(|byte| (byte - b'0') as usize)
.collect::<Vec<usize>>()
})
.collect();
Box::new(shortest_path(&map))
},
|input| {
let map: Vec<Vec<usize>> = input
.lines()
.map(|line| {
line.bytes()
.map(|byte| (byte - b'0') as usize)
.collect::<Vec<usize>>()
})
.collect();
Box::new(shortest_path(&stitch_map(&map)))
},
)
}
#[cfg(test)]
mod tests {
use crate::days::fifteen::stitch_map;
use super::shortest_path;
#[test]
fn example() {
let input = "1163751742
1381373672
2136511328
3694931569
7463417111
1319128137
1359912421
3125421639
1293138521
2311944581";
let map: Vec<Vec<usize>> = input
.lines()
.map(|line| {
line.bytes()
.map(|byte| (byte - b'0') as usize)
.collect::<Vec<usize>>()
})
.collect();
assert_eq!(shortest_path(&map), 40);
assert_eq!(shortest_path(&stitch_map(&map)), 315);
}
}