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const std = @import("std");
const Result = @import("util/aoc.zig").Result;
const MAX_HEIGHT = 100;
const Command = struct { From: u8, To: u8, Crates: u8 };
const Data = struct {
Commands: []Command,
Crates: [][MAX_HEIGHT]u8,
fn deinit(self: Data, allocator: std.mem.Allocator) void {
allocator.free(self.Commands);
allocator.free(self.Crates);
}
};
pub fn puzzle_1(allocator: std.mem.Allocator, input: []const u8) !Result {
var data = try parse_input(allocator, input);
defer data.deinit(allocator);
for (data.Commands) |*command| {
while (command.Crates > 0) : (command.Crates -= 1) {
const tmp = data.Crates[command.From][len(data.Crates[command.From]) - 1];
data.Crates[command.From][len(data.Crates[command.From]) - 1] = 0;
data.Crates[command.To][len(data.Crates[command.To])] = tmp;
}
}
return build_answer(allocator, data.Crates);
}
pub fn puzzle_2(allocator: std.mem.Allocator, input: []const u8) !Result {
var data = try parse_input(allocator, input);
defer data.deinit(allocator);
for (data.Commands) |*command| {
const crate_stack = blk: {
var r = std.mem.zeroes([MAX_HEIGHT]u8);
var idx: usize = 0;
while (command.Crates > 0) : (command.Crates -= 1) {
r[idx] = data.Crates[command.From][len(data.Crates[command.From]) - 1];
data.Crates[command.From][len(data.Crates[command.From]) - 1] = 0;
idx += 1;
}
break :blk r;
};
var crate_stack_height = len(crate_stack);
while (true) {
data.Crates[command.To][len(data.Crates[command.To])] = crate_stack[crate_stack_height];
if (crate_stack_height == 0) break;
crate_stack_height -= 1;
}
}
return build_answer(allocator, data.Crates);
}
fn build_answer(allocator: std.mem.Allocator, crates: [][MAX_HEIGHT]u8) !Result {
var i: usize = 0;
var r = try std.ArrayList(u8).initCapacity(allocator, crates.len);
while (i < crates.len) : (i += 1) {
r.appendAssumeCapacity(crates[i][len(crates[i]) - 1]);
}
return .{ .string = try r.toOwnedSlice() };
}
fn parse_input(allocator: std.mem.Allocator, input: []const u8) !Data {
var iter = std.mem.split(u8, input, "\n");
var floor: u8 = 0;
var rows: usize = 0;
while (iter.next()) |line| : (floor += 1) {
if (line[1] == '1') {
rows = (line.len + 1) / 4;
iter.reset();
break;
}
}
var crates = blk: {
var r = try std.ArrayList([MAX_HEIGHT]u8).initCapacity(allocator, rows);
var i: usize = 0;
while (i < rows) : (i += 1) r.appendAssumeCapacity(std.mem.zeroes([MAX_HEIGHT]u8));
break :blk try r.toOwnedSlice();
};
while (iter.next()) |line| : (floor -= 1) {
if (floor == 0) break;
var row: usize = 0;
var offset: usize = 1;
while (row < rows) : (row += 1) {
if (line[offset] != ' ')
crates[row][floor - 1] = line[offset];
offset += 4;
}
}
// There is an extra line between floor and commands
iter.index = iter.index.? + 1;
var commands = std.ArrayList(Command).init(allocator);
var i: usize = 0;
while (iter.next()) |line| : (i += 1) {
var command: Command = undefined;
var line_iter = std.mem.split(u8, line, " ");
_ = line_iter.next(); // move
command.Crates = try std.fmt.parseInt(u8, line_iter.next() orelse unreachable, 0);
_ = line_iter.next(); // from
command.From = try std.fmt.parseInt(u8, line_iter.next() orelse unreachable, 0) - 1;
_ = line_iter.next(); // to
command.To = try std.fmt.parseInt(u8, line_iter.next() orelse unreachable, 0) - 1;
try commands.append(command);
}
return .{ .Commands = try commands.toOwnedSlice(), .Crates = crates };
}
fn len(row: [MAX_HEIGHT]u8) usize {
for (row) |v, i| {
if (v == 0) {
if (i > 0) return i;
return 0;
}
}
unreachable;
}
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