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authorXander Bil <xander@biltopia.org>2024-12-09 01:09:46 +0100
committerXander Bil <xander@biltopia.org>2024-12-09 01:09:46 +0100
commit9938190da763a7de7d938f9a1c097bc026ac7b91 (patch)
treeab2160f3ea2a5787319643868ffda08ea24b1692 /src/day08.zig
parentbd982cf90112e274032385277906af3fae7efe24 (diff)
downloadaoc2024-9938190da763a7de7d938f9a1c097bc026ac7b91.tar.xz
aoc2024-9938190da763a7de7d938f9a1c097bc026ac7b91.zip
add solution day08
Diffstat (limited to 'src/day08.zig')
-rw-r--r--src/day08.zig123
1 files changed, 123 insertions, 0 deletions
diff --git a/src/day08.zig b/src/day08.zig
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+++ b/src/day08.zig
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+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});
+}