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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 {
if (std.mem.eql(u8, part, "1")) {
try part1(buffer, allocator);
} else {
try part2(buffer, allocator);
}
}
fn amount(line: []const u8, allocator: std.mem.Allocator) usize {
const match = mecha.oneOf(.{ mecha.string("XMAS"), mecha.string("SAMX") });
var rest = line;
var output: usize = 0;
while (rest.len > 0) {
_ = match.parse(allocator, rest) catch {
rest = rest[1..];
continue;
};
rest = rest[3..];
output += 1;
}
return output;
}
fn diagonal(list: []const []const u8, startr: usize, startc: usize, dirr: i32, dirc: i32, allocator: std.mem.Allocator) !usize {
var line = std.ArrayList(u8).init(allocator);
defer line.deinit();
const rows: i32 = @intCast(list.len);
const width: i32 = @intCast(list[0].len);
var r: i32 = @intCast(startr);
var c: i32 = @intCast(startc);
while (r >= 0 and c >= 0 and r < rows and c < width) {
try line.append(list[@intCast(r)][@intCast(c)]);
r += dirr;
c += dirc;
}
return amount(line.items, allocator);
}
fn part1(buffer: []const u8, allocator: std.mem.Allocator) !void {
var lines = std.mem.splitScalar(u8, buffer, '\n');
var list = std.ArrayList([]const u8).init(allocator);
defer list.deinit();
var sum: usize = 0;
while (lines.next()) |line| {
if (line.len > 0) {
try list.append(line);
sum += amount(line, allocator); // HORIZONTAL
}
}
for (0..list.items.len) |r| {
sum += try diagonal(list.items, r, 0, -1, 1, allocator); // UP-RIGHT
sum += try diagonal(list.items, r, 0, 1, 1, allocator); // DOWN-RIGHT
}
for (1..list.items[0].len) |c| {
sum += try diagonal(list.items, 0, c, 1, 1, allocator); // DOWN-RIGHT
sum += try diagonal(list.items, list.items.len - 1, c, -1, 1, allocator); // UP-RIGHT
}
for (0..list.items[0].len) |c| { // VERTICAL
sum += try diagonal(list.items, 0, c, 1, 0, allocator);
}
print("{d}\n", .{sum});
}
//------------------------------PART 2---------------------------------------
fn diagonal2(list: []const []const u8, startr: usize, startc: usize, dirr: i32, dirc: i32, allocator: std.mem.Allocator, hashmap: anytype) !usize {
var line = std.ArrayList(u8).init(allocator);
defer line.deinit();
const rows: i32 = @intCast(list.len);
const width: i32 = @intCast(list[0].len);
var output: usize = 0;
var r: i32 = @intCast(startr);
var c: i32 = @intCast(startc);
while (r >= 0 and c >= 0 and r < rows and c < width) {
try line.append(list[@intCast(r)][@intCast(c)]);
if (line.items.len >= 3 and (std.mem.eql(u8, line.items[line.items.len - 3 ..], "MAS") or std.mem.eql(u8, line.items[line.items.len - 3 ..], "SAM"))) {
if (hashmap.contains((r - dirr) * rows + (c - dirc))) {
output += 1;
} else {
try hashmap.put((r - dirr) * rows + (c - dirc), 1);
}
}
r += dirr;
c += dirc;
}
return output;
}
fn part2(buffer: []const u8, allocator: std.mem.Allocator) !void {
var map = std.AutoHashMap(i32, usize).init(allocator);
defer map.deinit();
var lines = std.mem.splitScalar(u8, buffer, '\n');
var list = std.ArrayList([]const u8).init(allocator);
defer list.deinit();
var sum: usize = 0;
while (lines.next()) |line| {
if (line.len > 0) {
try list.append(line);
}
}
for (0..list.items.len) |r| {
sum += try diagonal2(list.items, r, 0, -1, 1, allocator, &map); // UP-RIGHT
sum += try diagonal2(list.items, r, 0, 1, 1, allocator, &map); // DOWN-RIGHT
}
for (1..list.items[0].len) |c| {
sum += try diagonal2(list.items, 0, c, 1, 1, allocator, &map); // DOWN-RIGHT
sum += try diagonal2(list.items, list.items.len - 1, c, -1, 1, allocator, &map); // UP-RIGHT
}
print("{d}\n", .{sum});
}
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