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const std = @import("std");
const print = std.debug.print;
const assert = std.debug.assert;
const ArrayList = std.ArrayList;
const HashMap = std.HashMap;
const mem = std.mem;
const fin = mem.trim(u8, @embedFile("./input.txt"), &std.ascii.whitespace);
var gpa = std.heap.GeneralPurposeAllocator(.{}){};
const allocator = gpa.allocator();
const Map = []const []u8;
fn column_wise(map: Map, begin: isize, end: isize, step: isize) u64 {
const h = map.len;
const w = map[0].len;
var ans: u64 = 0;
for (0..w) |j| {
var next_free = begin;
var i = begin;
while (i != end) : (i += step) {
switch (map[@bitCast(i)][j]) {
'.' => {},
'O' => {
ans += h - @as(u64, @bitCast(next_free));
map[@bitCast(i)][j] = '.';
map[@bitCast(next_free)][j] = 'O';
next_free += step;
},
'#' => {
next_free = i + step;
},
else => unreachable,
}
}
}
return ans;
}
fn row_wise(map: Map, begin: isize, end: isize, step: isize) u64 {
const h = map.len;
var ans: u64 = 0;
for (0..h) |i| {
var next_free = begin;
var j = begin;
while (j != end) : (j += step) {
switch (map[i][@bitCast(j)]) {
'.' => {},
'O' => {
ans += h - i;
map[i][@bitCast(j)] = '.';
map[i][@bitCast(next_free)] = 'O';
next_free += step;
},
'#' => {
next_free = j + step;
},
else => unreachable,
}
}
}
return ans;
}
fn north(map: Map) u64 {
const h = map.len;
return column_wise(map, 0, @bitCast(h), 1);
}
fn west(map: Map) u64 {
const w = map[0].len;
return row_wise(map, 0, @bitCast(w), 1);
}
fn south(map: Map) u64 {
const h = map.len;
return column_wise(map, @bitCast(h - 1), -1, -1);
}
fn east(map: Map) u64 {
const w = map[0].len;
return row_wise(map, @bitCast(w - 1), -1, -1);
}
fn round(map: Map) u64 {
_ = north(map);
_ = west(map);
_ = south(map);
return east(map);
}
const MapCtx = struct {
pub fn hash(_: @This(), map: []const []u8) u64 {
var h: u64 = 0;
for (map, 0..) |row, i| {
for (row, 0..) |c, j| {
if (c == 'O') {
h ^= @shlExact(i, 16) | (j);
}
}
}
h *= 1231231557;
h ^= (h >> 32);
return h;
}
pub fn eql(_: @This(), lhs: []const []u8, rhs: []const []u8) bool {
for (lhs, rhs) |l, r| {
if (!mem.eql(u8, l, r)) {
return false;
}
}
return true;
}
};
fn mapdup(map: []const []const u8) Map {
const h = map.len;
const w = map[0].len;
const new = allocator.alloc([]u8, h) catch unreachable;
for (new, map) |*row, srcrow| {
row.* = allocator.alloc(u8, w) catch unreachable;
@memcpy(row.*, srcrow);
}
return new;
}
fn part1(map: []const []const u8) void {
const ans = north(mapdup(map));
print("{d}\n", .{ans});
}
fn part2(map_: []const []const u8) void {
var ans: u64 = 0;
var visited = HashMap(Map, u64, MapCtx, 80).init(allocator);
const map = mapdup(map_);
const reps = 1_000_000_000;
var upto: u64 = 0;
for (0..reps) |p| {
ans = round(map);
if (visited.get(map)) |s| {
const start = s;
const period = p - s;
upto = (reps - start - 1) % period;
break;
}
visited.put(mapdup(map), p) catch unreachable;
}
for (0..upto) |_| {
ans = round(map);
}
print("{d}\n", .{ans});
}
pub fn solve(map: []const []const u8) void {
part1(map);
part2(map);
}
pub fn main() !void {
var splitLines = mem.splitScalar(u8, fin, '\n');
var map = ArrayList([]const u8).init(allocator);
while (splitLines.next()) |line| {
try map.append(line);
}
solve(map.items);
}
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