1 files changed, 138 insertions, 0 deletions
diff --git a/day_05.zig b/day_05.zig
new file mode 100644
index 0000000..884fd81
--- /dev/null
+++ b/day_05.zig
@@ -0,0 +1,138 @@
+const std = @import("std");
+const Result = @import("util/aoc.zig").Result;
+
+const MAX_HEIGHT = 100;
+
+const Command = struct { From: u8, To: u8, Crates: u8 };
+const Data = struct {
+    Commands: []Command,
+    Crates: [][MAX_HEIGHT]u8,
+
+    fn deinit(self: Data, allocator: std.mem.Allocator) void {
+        allocator.free(self.Commands);
+        allocator.free(self.Crates);
+    }
+};
+
+pub fn puzzle_1(allocator: std.mem.Allocator, input: []const u8) !Result {
+    var data = try parse_input(allocator, input);
+    defer data.deinit(allocator);
+
+    for (data.Commands) |command| {
+        var command_crates = command.Crates;
+
+        while (command_crates > 0) : (command_crates -= 1) {
+            if (command_crates == 0) break;
+            const tmp = data.Crates[command.From][len(data.Crates[command.From]) - 1];
+            data.Crates[command.From][len(data.Crates[command.From]) - 1] = 0;
+            data.Crates[command.To][len(data.Crates[command.To])] = tmp;
+        }
+    }
+
+    return build_answer(allocator, data.Crates);
+}
+
+pub fn puzzle_2(allocator: std.mem.Allocator, input: []const u8) !Result {
+    var data = try parse_input(allocator, input);
+    defer data.deinit(allocator);
+
+    for (data.Commands) |command| {
+        var command_crates = command.Crates;
+
+        const crate_stack = blk: {
+            var r = std.mem.zeroes([MAX_HEIGHT]u8);
+            var idx: usize = 0;
+
+            while (command_crates > 0) : (command_crates -= 1) {
+                if (command_crates == 0) break;
+                r[idx] = data.Crates[command.From][len(data.Crates[command.From]) - 1];
+                data.Crates[command.From][len(data.Crates[command.From]) - 1] = 0;
+                idx += 1;
+            }
+
+            break :blk r;
+        };
+        var crate_stack_height = len(crate_stack);
+
+        while (true) {
+            data.Crates[command.To][len(data.Crates[command.To])] = crate_stack[crate_stack_height];
+            if (crate_stack_height == 0) break;
+            crate_stack_height -= 1;
+        }
+    }
+
+    return build_answer(allocator, data.Crates);
+}
+
+fn build_answer(allocator: std.mem.Allocator, crates: [][MAX_HEIGHT]u8) !Result {
+    var i: usize = 0;
+    var r = try std.ArrayList(u8).initCapacity(allocator, crates.len);
+    while (i < crates.len) : (i += 1) {
+        r.appendAssumeCapacity(crates[i][len(crates[i]) - 1]);
+    }
+
+    return .{ .string = r.toOwnedSlice() };
+}
+
+fn parse_input(allocator: std.mem.Allocator, input: []const u8) !Data {
+    var iter = std.mem.split(u8, input, "\n");
+
+    var floor: u8 = 0;
+    var rows: u8 = 0;
+
+    while (iter.next()) |line| : (floor += 1) {
+        if (line[1] == '1') {
+            var rows_iter = std.mem.splitBackwards(u8, line, " ");
+            _ = rows_iter.next();
+            rows = try std.fmt.parseInt(u8, rows_iter.next() orelse unreachable, 0);
+            iter.reset();
+            break;
+        }
+    }
+
+    var crates = blk: {
+        var r = try std.ArrayList([MAX_HEIGHT]u8).initCapacity(allocator, rows);
+        var i: usize = 0;
+        while (i < rows) : (i += 1) r.appendAssumeCapacity(std.mem.zeroes([MAX_HEIGHT]u8));
+        break :blk r.toOwnedSlice();
+    };
+
+    while (iter.next()) |line| : (floor -= 1) {
+        if (floor == 0) break;
+
+        var row: usize = 0;
+        var offset: usize = 1;
+        while (row < rows) : (row += 1) {
+            if (line[offset] != ' ')
+                crates[row][floor - 1] = line[offset];
+            offset += 4;
+        }
+    }
+
+    // There is an extra line between floor and commands
+    iter.index = iter.index.? + 1;
+    var commands = std.ArrayList(Command).init(allocator);
+    var i: usize = 0;
+    while (iter.next()) |line| : (i += 1) {
+        var command: Command = undefined;
+        var line_iter = std.mem.split(u8, line, " ");
+        _ = line_iter.next(); // move
+        command.Crates = try std.fmt.parseInt(u8, line_iter.next() orelse unreachable, 0);
+        _ = line_iter.next(); // from
+        command.From = try std.fmt.parseInt(u8, line_iter.next() orelse unreachable, 0) - 1;
+        _ = line_iter.next(); // to
+        command.To = try std.fmt.parseInt(u8, line_iter.next() orelse unreachable, 0) - 1;
+        try commands.append(command);
+    }
+    return .{ .Commands = commands.toOwnedSlice(), .Crates = crates };
+}
+
+fn len(row: [MAX_HEIGHT]u8) usize {
+    for (row) |v, i| {
+        if (v == 0) {
+            if (i > 0) return i;
+            return 0;
+        }
+    }
+    unreachable;
+}