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Use Dijkstra instead of A*

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The available distance heuristic doesn't save enough steps to offset its
overhead.
This commit is contained in:
Bert Peters
2021-12-15 18:29:08 +01:00
parent c3929a56d8
commit 9a4ac427e0
1 changed files with 3 additions and 8 deletions
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11
2021/src/day15.rs
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@@ -69,13 +69,13 @@ impl Map {
pub fn shortest_path(&self, start: Point, end: Point) -> u32 { pub fn shortest_path(&self, start: Point, end: Point) -> u32 {
let mut todo = BinaryHeap::new(); let mut todo = BinaryHeap::new();
todo.push(Reverse((Self::manhattan(start, end), 0, start))); todo.push(Reverse((0, start)));
let mut visited = vec![false; self.data.len()]; let mut visited = vec![false; self.data.len()];
let height = self.height() as i32; let height = self.height() as i32;
while let Some(Reverse((_, distance, pos))) = todo.pop() { while let Some(Reverse((distance, pos))) = todo.pop() {
if pos == end { if pos == end {
return distance; return distance;
} }
@@ -106,9 +106,8 @@ impl Map {
} }
let new_distance = distance + self.data[index] as u32; let new_distance = distance + self.data[index] as u32;
let new_guess = Self::manhattan(new, end) + new_distance;
todo.push(Reverse((new_guess, new_distance, new))); todo.push(Reverse((new_distance, new)));
} }
} }
} }
@@ -116,10 +115,6 @@ impl Map {
panic!("No route found from {:?} to {:?}", start, end); panic!("No route found from {:?} to {:?}", start, end);
} }
fn manhattan((xa, ya): Point, (xb, yb): Point) -> u32 {
(xa - xb).abs() as u32 + (ya - yb).abs() as u32
}
pub fn height(&self) -> usize { pub fn height(&self) -> usize {
self.data.len() / self.width self.data.len() / self.width
} }