diff options
| -rw-r--r-- | main.zig | 2 | ||||
| -rw-r--r-- | src/day08.zig | 123 |
2 files changed, 125 insertions, 0 deletions
@@ -8,6 +8,7 @@ const day04 = @import("src/day04.zig"); const day05 = @import("src/day05.zig"); const day06 = @import("src/day06.zig"); const day07 = @import("src/day07.zig"); +const day08 = @import("src/day08.zig"); pub fn main() !void { if (std.os.argv.len != 3) { @@ -43,6 +44,7 @@ pub fn main() !void { 5 => day05.solve(args[2], buffer, allocator), 6 => day06.solve(args[2], buffer, allocator), 7 => day07.solve(args[2], buffer, allocator), + 8 => day08.solve(args[2], buffer, allocator), else => print("Day not yet implemented", .{}), }; } diff --git a/src/day08.zig b/src/day08.zig new file mode 100644 index 0000000..2e356d9 --- /dev/null +++ b/src/day08.zig @@ -0,0 +1,123 @@ +const std = @import("std"); +const mecha = @import("mecha"); +const print = std.debug.print; + +pub fn solve(part: []u8, buffer: []u8, allocator: std.mem.Allocator) !void { + var lookup: [256]std.ArrayList(std.meta.Tuple(&.{ i32, i32 })) = undefined; + for (&lookup) |*element| { + element.* = std.ArrayList(std.meta.Tuple(&.{ i32, i32 })).init(allocator); + errdefer element.*.deinit(); + } + + var lines = std.mem.splitScalar(u8, buffer, '\n'); + const width: usize = lines.next().?.len; + lines.reset(); + const distinct: [][]bool = try allocator.alloc([]bool, width * width); + defer allocator.free(distinct); + for (distinct) |*r| { + r.* = try allocator.alloc(bool, width); + @memset(r.*, false); + } + + if (std.mem.eql(u8, part, "1")) { + try part1(&lookup, distinct, &lines, width); + } else { + try part2(&lookup, distinct, &lines, width); + } + + for (&lookup) |*element| { + element.*.deinit(); + } + + for (distinct) |r| { + allocator.free(r); + } +} + +fn part1(lookup: *[256]std.ArrayList(std.meta.Tuple(&.{ i32, i32 })), distinct: [][]bool, lines: *std.mem.SplitIterator(u8, .scalar), width: usize) !void { + var row: i32 = 0; + var total_distinct: usize = 0; + while (lines.next()) |line| : (row += 1) { + if (line.len == 0) break; + + var col: i32 = 0; + for (line) |item| { + if (item == '.' or item == '#') { + col += 1; + continue; + } + + for (lookup[item].items) |antenna| { + const diffr = row - antenna[0]; + const diffc = col - antenna[1]; + + const newr1 = antenna[0] - diffr; + const newc1 = antenna[1] - diffc; + if (newr1 >= 0 and newc1 >= 0 and newc1 < width and !distinct[@intCast(newr1)][@intCast(newc1)]) { + distinct[@intCast(newr1)][@intCast(newc1)] = true; + total_distinct += 1; + } + + const newr2 = row + diffr; + const newc2 = col + diffc; + if (newr2 < width and newc2 >= 0 and newc2 < width and !distinct[@intCast(newr2)][@intCast(newc2)]) { + distinct[@intCast(newr2)][@intCast(newc2)] = true; + total_distinct += 1; + } + } + + try lookup[item].append(.{ row, col }); + col += 1; + } + } + + print("{d}\n", .{total_distinct}); +} + +fn part2(lookup: *[256]std.ArrayList(std.meta.Tuple(&.{ i32, i32 })), distinct: [][]bool, lines: *std.mem.SplitIterator(u8, .scalar), width: usize) !void { + var row: i32 = 0; + var total_distinct: usize = 0; + while (lines.next()) |line| : (row += 1) { + if (line.len == 0) break; + + var col: i32 = 0; + for (line) |item| { + if (item == '.' or item == '#') { + col += 1; + continue; + } + + for (lookup[item].items) |antenna| { + const diffr = row - antenna[0]; + const diffc = col - antenna[1]; + + var newr1 = antenna[0]; + var newc1 = antenna[1]; + while (newr1 >= 0 and newc1 >= 0 and newc1 < width) { + if (!distinct[@intCast(newr1)][@intCast(newc1)]) { + distinct[@intCast(newr1)][@intCast(newc1)] = true; + total_distinct += 1; + } + newr1 -= diffr; + newc1 -= diffc; + } + + var newr2 = row; + var newc2 = col; + while (newr2 < width and newc2 >= 0 and newc2 < width) { + if (!distinct[@intCast(newr2)][@intCast(newc2)]) { + distinct[@intCast(newr2)][@intCast(newc2)] = true; + total_distinct += 1; + } + newr2 += diffr; + newc2 += diffc; + } + } + + try lookup[item].append(.{ row, col }); + col += 1; + } + } + + print("{d}\n", .{total_distinct}); +} |