scubbo/advent-of-code-2024
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Refactor solutions to 20 to use common code

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This commit is contained in:
Jack Jackson 2025-01-23 21:16:24 -08:00
parent d4b5ba7279
commit 171a276de3
1 changed files with 3 additions and 61 deletions
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64
solutions/20.zig
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@ -21,9 +21,6 @@ pub fn main() !void {
// * Find all cheats
// * For each cheat:
// * Time saved is basic time - (time-from-start-to-start-of-cheat - time-from-end-of-cheat-to-end)
//
// Implementation is not yet complete! So far I've only implemented the first bullet, because building a generic
// implementation of Dijkstra's was an _ARSE_ - the rest can happen tomorrow!
fn partOne(is_test_case: bool, debug: bool, allocator: std.mem.Allocator) !u32 {
const input_file = try util.getInputFile("20", is_test_case);
const data = try util.readAllInputWithAllocator(input_file, allocator);
@ -67,10 +64,10 @@ fn partOne(is_test_case: bool, debug: bool, allocator: std.mem.Allocator) !u32 {
defer distances_map_from_end.deinit();
const shortest_non_cheating_path = distances_map.get(end_point).?;
const cheats = findAllPossibleCheats(map, allocator);
defer allocator.free(cheats);
var cheats = findCheatsWithMaximumLength(map, 2, allocator);
defer cheats.deinit();
var scored_cheats = scoreCheats(cheats, shortest_non_cheating_path, distances_map, distances_map_from_end, debug, allocator);
var scored_cheats = scoreCheatsWithVariableLength(cheats, shortest_non_cheating_path, distances_map, distances_map_from_end, debug, allocator);
defer scored_cheats.deinit();
var total: u32 = 0;
@ -141,61 +138,6 @@ fn findPoint(data: [][]u8, char: u8) Point {
unreachable;
}
fn findAllPossibleCheats(data: [][]u8, allocator: std.mem.Allocator) []Cheat {
var set = std.AutoHashMap(Cheat, void).init(allocator);
defer set.deinit();
for (data, 0..) |line, y| {
for (line, 0..) |c, x| {
var shouldPrintDebugStatements = false;
if (y == 7 and x == 7) {
shouldPrintDebugStatements = true;
}
log("In 7/7 case\n", .{}, shouldPrintDebugStatements);
if (c != '.') {
continue;
}
if (x + 2 < data[0].len and data[y][x + 2] == '.') {
set.put(Cheat{ .start = Point{ .x = x, .y = y }, .end = Point{ .x = x + 2, .y = y } }, {}) catch unreachable;
}
if (x >= 2 and data[y][x - 2] == '.') {
set.put(Cheat{ .start = Point{ .x = x, .y = y }, .end = Point{ .x = x - 2, .y = y } }, {}) catch unreachable;
} else {}
if (y + 2 < data.len and data[y + 2][x] == '.') {
set.put(Cheat{ .start = Point{ .x = x, .y = y }, .end = Point{ .x = x, .y = y + 2 } }, {}) catch unreachable;
}
if (y >= 2 and data[y - 2][x] == '.') {
set.put(Cheat{ .start = Point{ .x = x, .y = y }, .end = Point{ .x = x, .y = y - 2 } }, {}) catch unreachable;
}
}
}
var output = std.ArrayList(Cheat).init(allocator);
var set_iter = set.keyIterator();
while (set_iter.next()) |p| {
output.append(p.*) catch unreachable;
}
return output.toOwnedSlice() catch unreachable;
}
fn scoreCheats(cheats: []Cheat, base_lowest_time: u32, distances_from_start: std.AutoHashMap(Point, u32), distances_from_end: std.AutoHashMap(Point, u32), debug: bool, allocator: std.mem.Allocator) std.AutoHashMap(Cheat, i64) {
var output = std.AutoHashMap(Cheat, i64).init(allocator);
for (cheats) |cheat| {
output.put(cheat, scoreCheat(cheat, base_lowest_time, distances_from_start, distances_from_end, debug)) catch unreachable;
}
return output;
}
// Note - `i64`, rather than `u32`, because a cheat might make the time _longer_!
fn scoreCheat(cheat: Cheat, base_lowest_time: u32, distances_from_start: std.AutoHashMap(Point, u32), distances_from_end: std.AutoHashMap(Point, u32), debug: bool) i64 {
const distance_from_start = distances_from_start.get(cheat.start).?;
const distance_from_end = distances_from_end.get(cheat.end).?;
const total_time_with_cheat = distance_from_start + distance_from_end + 2;
log("DEBUG - total_time_with_cheat for {s} is {} - based on {} and {}\n", .{ cheat, total_time_with_cheat, distance_from_start, distance_from_end }, debug);
return @as(i64, base_lowest_time) - @as(i64, total_time_with_cheat);
}
test "partOne" {
var gpa = std.heap.GeneralPurposeAllocator(.{}){};
defer _ = gpa.deinit();