aoc/2021/06/part-two.zig


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const parseUnsigned = std.fmt.parseUnsigned;
const print = std.debug.print;
const rotate = std.mem.rotate;
const std = @import("std");
const tokenize = std.mem.tokenize;

const input = @embedFile("input");

pub fn main() !void {
    var timer = [_]usize{ 0 } ** 9;
    defer print("{}\n", .{ @reduce(.Add, @as(@Vector(9, usize), timer)) });

    var list = tokenize(input[0..input.len-1], ",");
    while (list.next()) |i|
        timer[try parseUnsigned(usize, i, 10)] += 1;

    var i: usize = 0;
    while (i < 256) : (i += 1) {
        rotate(usize, timer[0..], 1);
        timer[6] += timer[8];
    }
}