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Finish day07, part 2

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ktkk 2025-12-07 20:26:53 +00:00
parent cc35a07724
commit beca41e511
1 changed files with 65 additions and 18 deletions
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83
src/days/day07.zig
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@ -35,44 +35,73 @@ pub fn run(allocator: std.mem.Allocator) !void {
std.debug.print("{s}\n", .{first_line}); std.debug.print("{s}\n", .{first_line});
const previous_line = try allocator.alloc(u8, line_len); const previous_line = try allocator.alloc(Cell, line_len);
defer allocator.free(previous_line); defer allocator.free(previous_line);
var accumulator: usize = 0;
var i: usize = 0; var i: usize = 0;
while (lines.next()) |line| { while (lines.next()) |line| {
defer i += 1; defer i += 1;
const current_line = try allocator.alloc(u8, line_len); const current_line = try allocator.alloc(Cell, line_len);
defer allocator.free(current_line); defer allocator.free(current_line);
@memcpy(current_line, line); for (line, 0..) |c, ci| {
switch (c) {
'.' => current_line[ci] = .empty,
'^' => current_line[ci] = .splitter,
else => unreachable, // There shouldn't be beams on this line yet!
}
}
defer @memcpy(previous_line, current_line); defer @memcpy(previous_line, current_line);
defer std.debug.print("{s}\n", .{current_line}); defer {
for (current_line) |cell| {
std.debug.print("{f}", .{cell});
}
std.debug.print("\n", .{});
}
if (i == 0) { if (i == 0) {
std.debug.assert(current_line[starting_position] == '.'); std.debug.assert(current_line[starting_position] == .empty);
current_line[starting_position] = '|'; current_line[starting_position] = .{ .beam = .{ .timelines = 1 } };
continue; continue;
} }
for (line, 0..) |c, ci| { for (current_line, 0..) |cell, celli| {
if (previous_line[ci] == '|') { const previous_cell = previous_line[celli];
if (c == '.') { if (previous_cell == .beam) {
current_line[ci] = '|'; if (cell == .empty) {
} else if (c == '^') { current_line[celli] = .{ .beam = .{ .timelines = previous_cell.beam.timelines } };
accumulator += 1; } else if (cell == .splitter) {
if (ci != 0 and current_line[ci - 1] == '.') { if (celli != 0) {
current_line[ci - 1] = '|'; const left = current_line[celli - 1];
if (left == .empty) {
current_line[celli - 1] = .{ .beam = .{ .timelines = previous_cell.beam.timelines } };
} else if (left == .beam) {
current_line[celli - 1] = .{ .beam = .{ .timelines = left.beam.timelines + previous_cell.beam.timelines } };
} }
if (ci != line_len - 1 and current_line[ci + 1] == '.') { }
current_line[ci + 1] = '|'; if (celli != line_len - 1) {
const right = current_line[celli + 1];
if (right == .empty) {
current_line[celli + 1] = .{ .beam = .{ .timelines = previous_cell.beam.timelines } };
} else if (right == .beam) {
current_line[celli + 1] = .{ .beam = .{ .timelines = right.beam.timelines + previous_cell.beam.timelines } };
}
}
} else if (cell == .beam and previous_cell == .beam) {
current_line[celli] = .{ .beam = .{ .timelines = cell.beam.timelines + previous_cell.beam.timelines } };
} }
} }
} }
} }
var accumulator: usize = 0;
for (previous_line) |cell| {
accumulator += switch (cell) {
.empty, .splitter => 0,
.beam => |beam| beam.timelines,
};
} }
var buffer: [8]u8 = undefined; var buffer: [8]u8 = undefined;
@ -84,3 +113,21 @@ pub fn run(allocator: std.mem.Allocator) !void {
try stdout.flush(); try stdout.flush();
} }
const Cell = union(enum) {
empty: void,
splitter: void,
beam: struct {
timelines: usize,
},
const Self = @This();
pub fn format(self: Cell, w: *std.io.Writer) std.io.Writer.Error!void {
switch (self) {
.empty => try w.print(".", .{}),
.splitter => try w.print("^", .{}),
.beam => |beam| try w.print("{d}", .{beam.timelines}),
}
}
};