solutions day3 and 4

1 files changed, 63 insertions, 0 deletions

diff --git a/src/day03.zig b/src/day03.zig
new file mode 100644
index 0000000..0a5e27e
--- /dev/null
+++ b/src/day03.zig
@@ -0,0 +1,63 @@
+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 part1(buffer: []const u8, allocator: std.mem.Allocator) !void {
+    const mul = mecha.combine(.{ mecha.string("mul(").discard(), mecha.int(usize, .{}), mecha.ascii.char(',').discard(), mecha.int(usize, .{}), mecha.ascii.char(')').discard() });
+
+    var sum: usize = 0;
+    var rest = buffer;
+    while (rest.len > 0) {
+        const result = mul.parse(allocator, rest) catch {
+            rest = rest[1..];
+            continue;
+        };
+        sum += result.value[0] * result.value[1];
+        rest = result.rest;
+    }
+
+    print("{d}", .{sum});
+}
+
+// UGLY
+fn part2(buffer: []const u8, allocator: std.mem.Allocator) !void {
+    const mul = mecha.combine(.{ mecha.string("mul(").discard(), mecha.int(usize, .{}), mecha.ascii.char(',').discard(), mecha.int(usize, .{}), mecha.ascii.char(')').discard() });
+
+    const dont = mecha.string("don't()");
+    const do = mecha.string("do()");
+
+    var sum: usize = 0;
+    var rest = buffer;
+    var disabled = false;
+    while (rest.len > 0) {
+        if (disabled) {
+            _ = do.parse(allocator, rest) catch {
+                rest = rest[1..];
+                continue;
+            };
+            disabled = false;
+        } else {
+            const result = mul.parse(allocator, rest) catch {
+                const result = dont.parse(allocator, rest) catch {
+                    rest = rest[1..];
+                    continue;
+                };
+                rest = result.rest;
+                disabled = true;
+                continue;
+            };
+            sum += result.value[0] * result.value[1];
+            rest = result.rest;
+        }
+    }
+
+    print("{d}", .{sum});
+}