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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 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});
}
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