2022-10 in zig

2022/10-cathode-ray-tube/first.zig

@@ -0,0 +1,37 @@
+const std = @import("std");
+
+const example = @embedFile("example");
+const input = @embedFile("input");
+
+pub fn main() anyerror!void {
+    try std.testing.expectEqual(solve(example), 13140);
+    const result = solve(input);
+    try std.io.getStdOut().writer().print("{}\n", .{result});
+}
+
+fn solve(puzzle: []const u8) i64 {
+    var it = std.mem.tokenize(u8, puzzle, "\n");
+    var tot: i64 = 0;
+    var cycle: i64 = 1;
+    var x: i64 = 1;
+    var line: []const u8 = undefined;
+    var prev: ?i64 = null;
+    // process input
+    while (cycle <= 220) : (cycle += 1) {
+        if (@mod(cycle - 20, 40) == 0) {
+            tot += x * cycle;
+        }
+        if (prev) |p| { // cpu is busy adding
+            x += p;
+            prev = null;
+        } else { // read another instruction
+            line = it.next() orelse break;
+            if (line[0] == 'a') {
+                var elts = std.mem.split(u8, line, " ");
+                _ = elts.next() orelse unreachable;
+                prev = std.fmt.parseInt(i64, elts.next() orelse unreachable, 10) catch unreachable;
+            }
+        }
+    }
+    return tot;
+}