const std = @import("std"); fn StackList(comptime T: type, comptime capacity_type: type, comptime capacity: capacity_type) type { return struct { const Self = @This(); mem: [capacity]T, length: capacity_type, fn add(self: *Self, value: T) void { self.mem[self.length] = value; self.length += 1; } fn has(self: *Self, needle: T) bool { for (0..self.length) |i| { if (self.mem[i] == needle) { return true; } } return false; } fn getMutableSlice(self: *Self) []T { return (&self.mem)[0..self.length]; } fn getSlice(self: *const Self) []const T { return self.mem[0..self.length]; } fn init() Self { return Self{ .mem = undefined, .length = 0, }; } }; } fn isMirroredHorizontallyAt(lines: []const []const u8, mirror_before: usize) bool { var a = mirror_before - 1; var b = mirror_before; while (a >= 0 and b < lines.len) { for (lines[a], lines[b]) |char_a, char_b| { if (char_a != char_b) { return false; } } if (a == 0) { break; } a -= 1; b += 1; } return true; } fn isMirroredVerticallyAt(lines: []const []const u8, mirror_before: usize) bool { for (lines) |line| { var a = mirror_before - 1; var b = mirror_before; while (a >= 0 and b < line.len) { if (line[a] != line[b]) { return false; } if (a == 0) { break; } a -= 1; b += 1; } } return true; } fn solveLines(lines: []const []const u8) usize { var result: usize = 0; var column: usize = 1; while (column < lines[0].len) : (column += 1) { if (isMirroredVerticallyAt(lines, column)) { result += column; } } var row: usize = 1; while (row < lines.len) : (row += 1) { if (isMirroredHorizontallyAt(lines, row)) { result += 100 * row; } } return result; } pub fn solveAll(reader: anytype) !usize { var result: usize = 0; while (true) { var allocator_buffer: [10000]u8 = undefined; var fba = std.heap.FixedBufferAllocator.init(&allocator_buffer); var allocator = fba.allocator(); var lines = StackList([]const u8, usize, 100).init(); var empty_line_reached = false; var line_buffer: [1000]u8 = undefined; while (try reader.readUntilDelimiterOrEof(&line_buffer, '\n')) |line| { if (line.len == 0) { empty_line_reached = true; break; } lines.add(try allocator.dupe(u8, line)); } result += solveLines(lines.getSlice()); if (!empty_line_reached) { return result; } } } pub fn main() !void { const stdout = std.io.getStdOut().writer(); const raw_in = std.io.getStdIn(); var buffered_reader = std.io.bufferedReader(raw_in.reader()); var reader = buffered_reader.reader(); const result = try solveAll(&reader); try stdout.print("{d}\n", .{result}); }