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refactor: 2024 Day 16 move shortestPath

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This commit is contained in:
Jeremy Kaplan 2024-12-23 14:21:05 -08:00
commit 9a389f5cfa
2 changed files with 85 additions and 85 deletions
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84
2024/src/aoc.zig
View file

@ -123,87 +123,3 @@ pub fn readAll(allocator: std.mem.Allocator, path: []const u8) ![]u8 {
return try file.readToEndAlloc(allocator, comptime 1 << 30);
}
pub fn shortestPath(
comptime State: type,
allocator: std.mem.Allocator,
ctx: State.Context,
start: State,
comptime withGraph: bool,
) !?(if (withGraph) struct { u64, std.AutoHashMap(State, AutoHashSet(State)) } else u64) {
const Entry = struct {
state: State,
cost: u64,
const Self = @This();
fn compare(_: void, a: Self, b: Self) std.math.Order {
return std.math.order(a.cost, b.cost);
}
};
var queue = std.PriorityQueue(Entry, void, comptime Entry.compare).init(allocator, {});
defer queue.deinit();
try queue.add(Entry{
.state = start,
.cost = 0,
});
var prev = std.AutoHashMap(State, AutoHashSet(State)).init(allocator);
defer if (!withGraph) {
prev.deinit();
var it = prev.valueIterator();
while (it.next()) |set| set.deinit();
};
var dist = std.AutoHashMap(State, u64).init(allocator);
defer dist.deinit();
try dist.put(start, 0);
while (queue.removeOrNull()) |entry| {
const u, const cost = .{ entry.state, entry.cost };
if (dist.get(u)) |best| {
if (best < cost) {
continue;
}
}
if (u.isGoal(ctx)) {
if (withGraph) {
return .{ cost, prev };
} else {
return cost;
}
}
var neighbors: std.ArrayList(State.Neighbor) = try u.neighbors(ctx);
defer neighbors.deinit();
for (neighbors.items) |neighbor| {
const v, const extra = .{ neighbor.next, neighbor.extra };
const alt = cost + extra;
if (dist.get(v)) |dv| {
if (alt > dv) {
continue;
}
}
var e = try prev.getOrPut(v);
if (!e.found_existing) {
e.value_ptr.* = AutoHashSet(State).init(allocator);
}
try e.value_ptr.put(u);
try dist.put(v, alt);
try queue.add(Entry{
.state = v,
.cost = alt,
});
}
}
return null;
}

86
2024/src/day16.zig
View file

@ -116,7 +116,7 @@ fn search(allocator: Allocator, grid: Grid) !struct { u64, u64 } {
.goal = goal,
};
const best, var graph: Map(State, Set(State)) = (try aoc.shortestPath(State, allocator, ctx, start, true)).?;
const best, var graph: Map(State, Set(State)) = (try shortestPath(State, allocator, ctx, start, true)).?;
defer graph.deinit();
defer {
var it = graph.valueIterator();
@ -317,3 +317,87 @@ const Grid = struct {
}
}
};
pub fn shortestPath(
comptime State: type,
allocator: std.mem.Allocator,
ctx: State.Context,
start: State,
comptime withGraph: bool,
) !?(if (withGraph) struct { u64, std.AutoHashMap(State, Set(State)) } else u64) {
const Entry = struct {
state: State,
cost: u64,
const Self = @This();
fn compare(_: void, a: Self, b: Self) std.math.Order {
return std.math.order(a.cost, b.cost);
}
};
var queue = std.PriorityQueue(Entry, void, comptime Entry.compare).init(allocator, {});
defer queue.deinit();
try queue.add(Entry{
.state = start,
.cost = 0,
});
var prev = std.AutoHashMap(State, Set(State)).init(allocator);
defer if (!withGraph) {
prev.deinit();
var it = prev.valueIterator();
while (it.next()) |set| set.deinit();
};
var dist = std.AutoHashMap(State, u64).init(allocator);
defer dist.deinit();
try dist.put(start, 0);
while (queue.removeOrNull()) |entry| {
const u, const cost = .{ entry.state, entry.cost };
if (dist.get(u)) |best| {
if (best < cost) {
continue;
}
}
if (u.isGoal(ctx)) {
if (withGraph) {
return .{ cost, prev };
} else {
return cost;
}
}
var neighbors: std.ArrayList(State.Neighbor) = try u.neighbors(ctx);
defer neighbors.deinit();
for (neighbors.items) |neighbor| {
const v, const extra = .{ neighbor.next, neighbor.extra };
const alt = cost + extra;
if (dist.get(v)) |dv| {
if (alt > dv) {
continue;
}
}
var e = try prev.getOrPut(v);
if (!e.found_existing) {
e.value_ptr.* = Set(State).init(allocator);
}
try e.value_ptr.put(u);
try dist.put(v, alt);
try queue.add(Entry{
.state = v,
.cost = alt,
});
}
}
return null;
}