day 1 Kot

src/days/day1.zig

@@ -0,0 +1,105 @@
+const std = @import("std");
+
+const parseInt = std.fmt.parseInt;
+
+// fn mightFail() anyerror!void
+//                ^^^^^^^^ we don't know the error, so any error might be returned
+// fn mightFail() !void
+//               ^  error type is inferred from the compiler
+// fn mightFail() error{OutOfMemory}!void
+//                ^^^^^^^^^^^^^^^^^^ error type is basically just an enum, in this case with only one value: OutOfMemory
+// Goals:
+//  x Write helper to load input text as buffer of some kind
+//  - Write test to assert for day 1 testinput
+
+// const as_cast: usize = @as(usize, @(u16, 1337));
+// const int_cast: isize = @intCast(@as(usize, 1337));
+// const ptr_cast: *usize = @ptrCast(@as(*isize, @ptrFromInt(0x1337)));
+// const float_from_int: f32 = @floatFromInt(1337);
+// const int_from_float: i32 = @intFromFloat(1337.66);
+// @alignCast, @constCast, @bitCast, @addrSpaceCast, @errorCast, @floatCast and @volatileCast i won't explain, as it's not
+// really necessary for now, and if you need it, you typically know it already
+
+pub fn day1pt1(dial_movements: []const u8) !usize {
+    var position: isize = 50; // without type hint: comptime_int
+    var counter: usize = 0;
+    var iter = std.mem.splitScalar(u8, dial_movements, '\n');
+    while (iter.next()) |line| {
+        if (line[0] == 'L') {
+            // slicing:
+            // line[1..] - returns new slice from position: 1 until end
+            // line[0..1] - returns a slice from start with length 1
+            // base 8 = octal
+            // base 10 = decimal
+            // base 16 = hex
+            //                 vvvvvvvvvvvvvvvv TYPE                                      v return value :3
+            // pub fn parseInt(comptime T: type, buf: []const u8, base: u8) ParseIntError!T
+            //                    vvvvvvvv do you think this function might fail?
+            position = position - try parseInt(isize, line[1..], 10);
+        } else { //         ^^ wollen wir wirklich ein u8 als PARSED RESULT haben?
+            position = position + try parseInt(isize, line[1..], 10);
+        }
+        position = @mod(position, 100);
+        if (position == 0) {
+            // post / pre increment / decrement doesn't exist
+            counter += 1;
+        }
+    }
+    return counter;
+}
+
+pub fn day1pt2(dial_movements: []const u8) !usize {
+    var position: isize = 50;
+    var counter: usize = 0;
+    var iter = std.mem.splitScalar(u8, dial_movements, '\n');
+    while (iter.next()) |line| {
+        const movement = try parseInt(isize, line[1..], 10);
+
+        if (line[0] == 'L') {
+            // Moving left (counter-clockwise)
+            if (position > 0 and movement >= position) { // greater equals to hit landings
+                // crossing 0
+                const crosses_after_first: usize = @intCast(@divFloor(movement - position, 100));
+                counter += 1 + crosses_after_first;
+            } else if (position == 0 and movement >= 100) {
+                // starting at 0 -> only full rotations
+                const full_rotations: usize = @intCast(@divFloor(movement, 100));
+                counter += full_rotations;
+            }
+            position = position - movement;
+        } else {
+            // Moving right (clockwise)
+            if (position > 0) {
+                const distance_to_zero = 100 - position;
+                if (movement >= distance_to_zero) {
+                    const crosses_after_first: usize = @intCast(@divFloor(movement - distance_to_zero, 100));
+                    counter += 1 + crosses_after_first;
+                }
+            } else if (position == 0 and movement >= 100) {
+                const full_rotations: usize = @intCast(@divFloor(movement, 100));
+                counter += full_rotations;
+            }
+            position = position + movement;
+        }
+
+        position = @mod(position, 100);
+    }
+    return counter;
+}
+
+test "Day 1 example testing" {
+    const example_input =
+        \\L68
+        \\L30
+        \\R48
+        \\L5
+        \\R60
+        \\L55
+        \\L1
+        \\L99
+        \\R14
+        \\L82
+    ;
+    try std.testing.expectEqual(try day1pt1(example_input), 3);
+    try std.testing.expectEqual(try day1pt2(example_input), 6);
+}

src/main.zig

@@ -1,10 +1,17 @@
 const std = @import("std");
-const aoc25 = @import("aoc25");
+const loadpuzzle = @import("utils/loadpuzzle.zig");
+const day1 = @import("days/day1.zig");
 
 pub fn main() !void {
     // Prints to stderr, ignoring potential errors.
+    const gpa = std.heap.smp_allocator;
+
     std.debug.print("All your {s} are belong to us.\n", .{"codebase"});
-    try aoc25.bufferedPrint();
+    std.debug.print("Starting AoC\n", .{});
+
+    const day1_input = try loadpuzzle.readFile(gpa, "puzzle_input/day1.txt");
+    std.debug.print("Day 1 Part 1: {any}\n", .{try day1.day1pt1(day1_input)});
+    std.debug.print("Day 1 Part 2: {any}\n", .{try day1.day1pt2(day1_input)});
 }
 
 test "simple test" {