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-rw-r--r--main.zig2
-rw-r--r--src/day10.zig32
-rw-r--r--src/day11.zig84
3 files changed, 102 insertions, 16 deletions
diff --git a/main.zig b/main.zig
index 1a4b7d3..73ca11d 100644
--- a/main.zig
+++ b/main.zig
@@ -11,6 +11,7 @@ const day07 = @import("src/day07.zig");
const day08 = @import("src/day08.zig");
const day09 = @import("src/day09.zig");
const day10 = @import("src/day10.zig");
+const day11 = @import("src/day11.zig");
pub fn main() !void {
if (std.os.argv.len != 3) {
@@ -49,6 +50,7 @@ pub fn main() !void {
8 => day08.solve(args[2], buffer, allocator),
9 => day09.solve(args[2], buffer, allocator),
10 => day10.solve(args[2], buffer, allocator),
+ 11 => day11.solve(args[2], buffer, allocator),
else => print("Day not yet implemented", .{}),
};
}
diff --git a/src/day10.zig b/src/day10.zig
index 13bed52..a0eb88d 100644
--- a/src/day10.zig
+++ b/src/day10.zig
@@ -125,16 +125,19 @@ fn part2(buffer: []const u8, allocator: std.mem.Allocator) !void {
@memset(grid[i], 0);
}
+ var list = std.ArrayList(std.meta.Tuple(&.{ usize, usize })).init(allocator);
+ defer list.deinit();
+
var row: usize = 0;
while (lines.next()) |line| {
if (line.len == 0) break;
for (line, 0..) |item, col| {
- if (item == '.') {
- grid[row][col] = 15;
- } else {
- grid[row][col] = item - '0';
+ grid[row][col] = item - '0';
+ if (item == '0') {
+ try list.append(.{ row, col });
}
}
+
row += 1;
}
@@ -143,19 +146,16 @@ fn part2(buffer: []const u8, allocator: std.mem.Allocator) !void {
for (0..width) |i| {
lookup[i] = try allocator.alloc(i32, width);
}
+
defer allocator.free(lookup);
- for (0..width) |r| {
- for (0..width) |c| {
- if (grid[r][c] == 0) {
- out += try dfs2(
- lookup,
- grid,
- @intCast(r),
- @intCast(c),
- -1,
- );
- }
- }
+ for (list.items) |zero| {
+ out += try dfs2(
+ lookup,
+ grid,
+ @intCast(zero[0]),
+ @intCast(zero[1]),
+ -1,
+ );
}
for (0..width) |i| {
diff --git a/src/day11.zig b/src/day11.zig
new file mode 100644
index 0000000..af04ac9
--- /dev/null
+++ b/src/day11.zig
@@ -0,0 +1,84 @@
+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 lines = std.mem.splitScalar(u8, buffer, '\n');
+ var split = std.mem.splitScalar(u8, lines.next().?, ' ');
+
+ var numbers = std.ArrayList(usize).init(allocator);
+ defer numbers.deinit();
+ while (split.next()) |n_string| {
+ try numbers.append(try std.fmt.parseInt(usize, n_string, 10));
+ }
+
+ if (std.mem.eql(u8, part, "1")) {
+ try part1(numbers, allocator);
+ } else {
+ try part2(numbers, allocator);
+ }
+}
+
+fn digits(int: usize) usize {
+ var count: usize = 0;
+ var temp = int;
+ while (temp > 0) {
+ temp /= 10;
+ count += 1;
+ }
+ return count;
+}
+
+fn recursive(number: usize, history: *std.AutoHashMap(std.meta.Tuple(&.{ usize, usize }), usize), depth: usize) !usize {
+ if (history.get(.{ number, depth })) |value| {
+ return value;
+ }
+
+ if (depth == 0) {
+ return 1;
+ }
+
+ var sum: usize = 0;
+ if (number == 0) {
+ sum = try recursive(1, history, depth - 1);
+ } else {
+ const n_digits = digits(number);
+ if (n_digits % 2 == 0) {
+ const p = std.math.pow(usize, 10, n_digits / 2);
+ const first = number / p;
+ const second = number % p;
+
+ sum += try recursive(first, history, depth - 1);
+ sum += try recursive(second, history, depth - 1);
+ } else {
+ sum += try recursive(number * 2024, history, depth - 1);
+ }
+ }
+
+ try history.put(.{ number, depth }, sum);
+ return sum;
+}
+
+fn part1(numbers: std.ArrayList(usize), allocator: std.mem.Allocator) !void {
+ var history = std.AutoHashMap(std.meta.Tuple(&.{ usize, usize }), usize).init(allocator);
+ defer history.deinit();
+
+ var total: usize = 0;
+ for (numbers.items) |number| {
+ total += try recursive(number, &history, 25);
+ }
+
+ print("{d}\n", .{total});
+}
+
+fn part2(numbers: std.ArrayList(usize), allocator: std.mem.Allocator) !void {
+ var history = std.AutoHashMap(std.meta.Tuple(&.{ usize, usize }), usize).init(allocator);
+ defer history.deinit();
+
+ var total: usize = 0;
+ for (numbers.items) |number| {
+ total += try recursive(number, &history, 75);
+ }
+
+ print("{d}\n", .{total});
+}