day 7 finished

lib/utils.zig

@@ -0,0 +1,179 @@
+const std = @import("std");
+
+pub const FileReader = struct {
+    const BufferedReader = std.io.BufferedReader(4096, std.fs.File.Reader);
+    const Reader = std.io.Reader(*BufferedReader, std.fs.File.Reader.Error, BufferedReader.read);
+
+    alloc: std.mem.Allocator,
+
+    file: std.fs.File,
+
+    buf_reader_ptr: *BufferedReader,
+
+    pub fn init(alloc: std.mem.Allocator, filename: []const u8) !FileReader {
+        const file = try std.fs.cwd().openFile(filename, .{});
+
+        const file_reader = file.reader();
+
+        const buf_reader_ptr = try alloc.create(BufferedReader);
+        buf_reader_ptr.* = std.io.bufferedReader(file_reader);
+
+        return .{
+            .alloc = alloc,
+            .file = file,
+            .buf_reader_ptr = buf_reader_ptr,
+        };
+    }
+
+    pub fn deinit(self: FileReader) void {
+        self.file.close();
+
+        self.alloc.destroy(self.buf_reader_ptr);
+    }
+
+    pub fn reader(self: FileReader) Reader {
+        return Reader{ .context = self.buf_reader_ptr };
+    }
+};
+
+pub fn LineReader(comptime ReaderType: type) type {
+    return struct {
+        const Self = @This();
+
+        reader: ReaderType,
+
+        line_buf: std.ArrayList(u8),
+
+        pub fn init(alloc: std.mem.Allocator, reader: ReaderType) Self {
+            const line_buf = std.ArrayList(u8).init(alloc);
+
+            return .{
+                .reader = reader,
+                .line_buf = line_buf,
+            };
+        }
+
+        pub fn deinit(self: *Self) void {
+            self.line_buf.deinit();
+        }
+
+        pub fn next(self: *Self) !?[]u8 {
+            self.line_buf.clearRetainingCapacity();
+
+            self.reader.streamUntilDelimiter(self.line_buf.writer(), '\n', 4096) catch |err| switch (err) {
+                error.EndOfStream => if (self.line_buf.items.len == 0) {
+                    // the first time we get an EndOfStream we return the content of the line_buf,
+                    // the second time we're finished
+                    return null;
+                },
+                else => return err,
+            };
+
+            return self.line_buf.items;
+        }
+    };
+}
+
+pub fn lineReader(alloc: std.mem.Allocator, reader: anytype) LineReader(@TypeOf(reader)) {
+    return LineReader(@TypeOf(reader)).init(alloc, reader);
+}
+
+pub fn NumberParser(comptime T: type) type {
+    return struct {
+        token_it: std.mem.TokenIterator(u8, .scalar),
+
+        pub fn next(self: *@This()) !?T {
+            if (self.token_it.next()) |tok| {
+                return try std.fmt.parseUnsigned(T, tok, 10);
+            }
+
+            return null;
+        }
+    };
+}
+
+pub fn numberParser(comptime T: type, input: []const u8) NumberParser(T) {
+    return NumberParser(T){ .token_it = std.mem.tokenizeScalar(u8, input, ' ') };
+}
+
+pub fn numberParserWithDelimiter(comptime T: type, input: []const u8, delimiter: u8) NumberParser(T) {
+    return NumberParser(T){ .token_it = std.mem.tokenizeScalar(u8, input, delimiter) };
+}
+
+pub fn rangeComptime(comptime n: usize) [n]usize {
+    var array: [n]usize = undefined;
+
+    for (0.., &array) |i, *elem| {
+        elem.* = i;
+    }
+
+    return array;
+}
+
+pub fn range(alloc: std.mem.Allocator, n: usize) ![]usize {
+    var array = try alloc.alloc(usize, n);
+
+    for (0..n) |i| {
+        array[i] = i;
+    }
+
+    return array;
+}
+
+pub fn printSlice(comptime T: type, slice: []const T) void {
+    if (slice.len == 0) {
+        std.debug.print("[ ]", .{});
+        return;
+    }
+
+    std.debug.print("[ ", .{});
+
+    for (slice[0 .. slice.len - 1]) |x| {
+        std.debug.print("{}, ", .{x});
+    }
+
+    std.debug.print("{} ]", .{slice[slice.len - 1]});
+}
+
+pub fn printlnSlice(comptime T: type, slice: []const T) void {
+    if (slice.len == 0) {
+        std.debug.print("[ ]\n", .{});
+        return;
+    }
+
+    std.debug.print("[ ", .{});
+
+    for (slice[0 .. slice.len - 1]) |x| {
+        std.debug.print("{}, ", .{x});
+    }
+
+    std.debug.print("{} ]\n", .{slice[slice.len - 1]});
+}
+
+pub fn num_digits(n: anytype) std.math.Log2Int(@TypeOf(n)) {
+    return std.math.log10_int(n) + 1;
+}
+
+test "num_digits" {
+    // try std.fmt.allocPrint(
+    //     std.testing.allocator,
+    //     "Expected {} to have 4 digit, but got {} instead",
+    //     .{ n, num_digits },
+    // );
+
+    for (2..10) |n| {
+        try std.testing.expectEqual(num_digits(n), 1);
+    }
+
+    for (10..100) |n| {
+        try std.testing.expectEqual(num_digits(n), 2);
+    }
+
+    for (100..1_000) |n| {
+        try std.testing.expectEqual(num_digits(n), 3);
+    }
+
+    for (1_000..10_000) |n| {
+        try std.testing.expectEqual(num_digits(n), 4);
+    }
+}