advent-of-code/2022/10-cathode-ray-tube/first.zig

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2022-12-10 14:23:31 +01:00
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;
}