115 lines
3.2 KiB
Zig
115 lines
3.2 KiB
Zig
const std = @import("std");
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const print = std.debug.print;
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const input = "890 0 1 935698 68001 3441397 7221 27";
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const numberT = u64;
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// Passed to a weird while loop instead of recurcive function because I run into limitation, too much recursion :/
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const Stone = struct {
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number: numberT,
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next: ?*Stone = null,
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fn step(self: *Stone, allocator: std.mem.Allocator) !void {
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var current = self;
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while (true) {
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if (current.number == 0) {
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current.number = 1;
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if (current.next) |right_stone| {
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current = right_stone;
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} else {
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break;
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}
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} else if (digitCount(current.number) % 2 == 0) {
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const new_value = splitNumber(current.number);
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const new_stone = try allocator.create(Stone);
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new_stone.* = Stone{ .number = new_value[1], .next = current.next };
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current.number = new_value[0];
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current.next = new_stone;
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if (new_stone.next) |right_stone| {
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current = right_stone;
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} else {
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break;
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}
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} else {
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current.number *= 2024;
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if (current.next) |right_stone| {
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current = right_stone;
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} else {
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break;
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}
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}
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}
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}
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fn printStone(self: Stone) void {
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print("{d} ", .{self.number});
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if (self.right) |right_stone| {
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right_stone.printStone();
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} else {
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print("\n", .{});
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}
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}
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fn count(self: *Stone, total: *usize) void {
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var current = self;
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while (true) {
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total.* += 1;
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if (current.next) |right_stone| {
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current = right_stone;
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} else {
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break;
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}
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}
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}
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};
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pub fn main() !void {
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var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
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defer arena.deinit();
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const allocator = arena.allocator();
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var iter = std.mem.splitAny(u8, input, " ");
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const first_stone = try allocator.create(Stone);
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first_stone.* = Stone{ .number = try std.fmt.parseInt(numberT, iter.next().?, 10) };
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var last_stone = first_stone;
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while (iter.next()) |number| {
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const new_stone = try allocator.create(Stone);
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new_stone.* = Stone{ .number = try std.fmt.parseInt(numberT, number, 10) };
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last_stone.next = new_stone;
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last_stone = new_stone;
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}
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for (0..25) |_| try first_stone.step(allocator);
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var total: usize = 0;
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first_stone.count(&total);
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try std.testing.expectEqual(194782, total);
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}
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fn digitCount(num: numberT) usize {
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if (num == 0) return 1;
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var n = num;
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var count: usize = 0;
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while (n != 0) : (n = @divFloor(n, 10)) {
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count += 1;
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}
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return count;
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}
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fn splitNumber(num: numberT) [2]numberT {
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const numDigits = digitCount(num);
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const halfDigits = numDigits / 2;
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var divisor: numberT = 1;
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for (halfDigits) |_| {
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divisor *= 10;
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}
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const left = @divFloor(num, divisor);
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const right = num % divisor;
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return [2]numberT{ left, right };
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}
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