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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 step = [_][2]i64{
[2]i64{ -1, 0 },
[2]i64{ 0, 1 },
[2]i64{ 1, 0 },
[2]i64{ 0, -1 },
};
const Beam = struct {
i: isize,
j: isize,
d: usize,
pub inline fn next(self: @This()) Beam {
return self.nextd(self.d);
}
pub inline fn prev(self: @This()) Beam {
return Beam{
.i = self.i - step[self.d][0],
.j = self.j - step[self.d][1],
.d = self.d,
};
}
pub inline fn nextd(self: @This(), d: usize) Beam {
return Beam{
.i = self.i + step[d][0],
.j = self.j + step[d][1],
.d = d,
};
}
pub const Ctx = struct {
pub fn hash(_: @This(), b: Beam) u64 {
return @bitCast(b.i << 16 | b.j << 8 | @as(isize, @bitCast(b.d)));
}
pub fn eql(_: @This(), lhs: Beam, rhs: Beam) bool {
return lhs.i == rhs.i and lhs.j == rhs.j and lhs.d == rhs.d;
}
};
// ignore direction when comparing beams
pub const Ctx2 = struct {
pub fn hash(_: @This(), b: Beam) u64 {
return @bitCast(b.i << 8 | b.j);
}
pub fn eql(_: @This(), lhs: Beam, rhs: Beam) bool {
const res = lhs.i == rhs.i and lhs.j == rhs.j;
return res;
}
};
};
var edgesVisited = HashMap(Beam, void, Beam.Ctx2, 80).init(allocator);
fn dfs(grid: []const []const u8, start: Beam) !u64 {
if (edgesVisited.get(start) != null) {
return 0;
}
const w = grid[0].len;
const h = grid.len;
var beams = ArrayList(Beam).init(allocator);
var visited = HashMap(Beam, void, Beam.Ctx, 80).init(allocator);
var uniq = HashMap(Beam, void, Beam.Ctx2, 80).init(allocator);
defer {
beams.deinit();
uniq.deinit();
visited.deinit();
}
try beams.append(start);
while (beams.items.len > 0) {
var curr = beams.pop();
while (0 <= curr.i and curr.i < h and 0 <= curr.j and curr.j < w) {
if ((try visited.getOrPut(curr)).found_existing) {
break;
}
const c = grid[@bitCast(curr.i)][@bitCast(curr.j)];
switch (c) {
'|' => {
try beams.append(curr.nextd(2));
curr = curr.nextd(0);
},
'-' => {
try beams.append(curr.nextd(3));
curr = curr.nextd(1);
},
'\\' => {
const d = (curr.d + if (curr.d & 1 != 0) @as(usize, 1) else @as(usize, 3)) % 4;
curr = curr.nextd(d);
},
'/' => {
const d = (curr.d + if (curr.d & 1 != 0) @as(usize, 3) else @as(usize, 1)) % 4;
curr = curr.nextd(d);
},
'.' => {
curr = curr.next();
},
else => unreachable,
}
} else { // finished by hitting an edge
try edgesVisited.put(curr.prev(), {});
}
}
var it = visited.keyIterator();
while (it.next()) |k| {
try uniq.put(k.*, {});
}
return uniq.count();
}
pub fn solve(grid: []const []const u8) !void {
const h = grid.len;
const w = grid[0].len;
const part1 = try dfs(grid, Beam{ .i = 0, .j = 0, .d = 1 });
print("{d}\n", .{part1});
var part2: u64 = 0;
for (0..h) |i_| {
const i: i64 = @bitCast(i_);
part2 = @max(part2, try dfs(grid, .{ .i = i, .j = 0, .d = 1 }));
part2 = @max(part2, try dfs(grid, .{ .i = i, .j = @bitCast(w - 1), .d = 3 }));
}
for (0..w) |j_| {
const j: i64 = @bitCast(j_);
part2 = @max(part2, try dfs(grid, .{ .i = 0, .j = j, .d = 2 }));
part2 = @max(part2, try dfs(grid, .{ .i = @bitCast(h - 1), .j = j, .d = 0 }));
}
print("{d}\n", .{part2});
}
pub fn main() !void {
var splitLines = mem.splitScalar(u8, fin, '\n');
var grid = ArrayList([]const u8).init(allocator);
while (splitLines.next()) |line| {
try grid.append(line);
}
try solve(grid.items);
}
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