1 files changed, 73 insertions, 0 deletions
diff --git a/day1/zig/src/main.zig b/day1/zig/src/main.zig
new file mode 100644
index 0000000..6520d5f
--- /dev/null
+++ b/day1/zig/src/main.zig
@@ -0,0 +1,73 @@
+const std = @import("std");
+const mem = std.mem;
+const math = std.math;
+
+pub fn main() !void {
+    const input: []const u8 = @embedFile("input.txt");
+    const part1, const part2 = try problem(input);
+    std.debug.print("Part 1: {}\n", .{part1});
+    std.debug.print("Part 2: {}\n", .{part2});
+}
+
+fn problem(input: []const u8) !struct { u64, u64 } {
+    const lines: mem.TokenIterator(u8, .scalar) = mem.tokenizeScalar(u8, input, '\n');
+    const part1: u64 = try p1(lines);
+    const part2: u64 = try p2(lines);
+    return .{ part1, part2 };
+}
+
+fn parseline(l: []const u8) !i64 {
+    return switch (l[0]) {
+        'L' => try std.fmt.parseInt(i64, l[1..], 10),
+        'R' => - try std.fmt.parseInt(i64, l[1..], 10),
+        else => error{InvalidLine}.InvalidLine,
+    };
+}
+
+inline fn rotatepos(pos: u32, n: i64) u32 {
+    return @truncate(@abs(@mod(pos + n, 100)));
+}
+
+fn countzeros(pos: u64, n: i64) u64 {
+    var zeros: u64 = 0;
+    var x: u32 = @intCast(pos);
+    var clicks: u64 = @abs(n);
+    const y: i64 = if (n < 0) -1 else 1;
+    while (clicks > 0) : (clicks -= 1){
+        x = rotatepos(x, y);
+        if (x == 0) zeros += 1;
+    }
+    return zeros;
+}
+
+fn p1(constLines: mem.TokenIterator(u8, .scalar)) !u64 {
+    var pos: u32 = 50;
+    var zeros: u64 = 0;
+    var lines = constLines;
+    while (lines.next()) |line| {
+        pos = rotatepos(pos, try parseline(line));
+        if (pos == 0) zeros += 1;
+    }
+    return zeros;
+}
+
+fn p2(constLines: mem.TokenIterator(u8, .scalar)) !u64 {
+    var pos: u32 = 50;
+    var zeros: u64 = 0;
+    var lines = constLines;
+    while (lines.next()) |line| {
+        const n = try parseline(line);
+        zeros += countzeros(pos, n);
+        pos = rotatepos(pos, n);
+    }
+    return zeros;
+}
+
+test "Sample Input" {
+    const input: []const u8 = @embedFile("input_sample.txt");
+    const part1, const part2 = try problem(input);
+    std.debug.print("Part 1: {}\n", .{part1});
+    std.debug.print("Part 2: {}\n", .{part2});
+    try std.testing.expectEqual(3, part1);
+    try std.testing.expectEqual(6, part2);
+}