1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
|
const std = @import("std");
const Result = @import("util/aoc.zig").Result;
pub fn puzzle_1(input: []const u8) Result {
var iter = std.mem.split(u8, input, "\n");
var count: u16 = 0;
while (iter.next()) |line| {
var p1: u64 = 0;
var p2: u64 = 0;
// A note to whoever reads this in the future
// A to Z -> 65 to 90
// a to z -> 97 to 122
//
// u64 is ok
// 90 - 65 + 122 - 97 = 50
for (line[0 .. line.len / 2]) |_, i| {
p1 |= @as(u64, 1) << @intCast(u6, line[i] - 65); // 65 == 'A'
p2 |= @as(u64, 1) << @intCast(u6, line[i + line.len / 2] - 65);
}
// Example
//
// p1: 0000000101100010001000110000000000011000000011000010000100
// p2: 1000001000000000000110000000000000000001011001100001100000
//
// &: 0000000000000000000000000000000000000000000001000000000000 = 46 0s
//
// 65 + 63 - 46 = 82 = R
count += char_to_priority(@intCast(u8, 65 + 63) - @clz(p1 & p2));
}
return .{ .int = count };
}
pub fn puzzle_2(input: []const u8) Result {
var iter = std.mem.split(u8, input, "\n");
var count: u16 = 0;
mainLoop: while (true) {
var parts = std.mem.zeroes([3]u64);
for (parts) |*p| {
const line = iter.next() orelse break :mainLoop;
for (line) |_, i| {
p.* |= @as(u64, 1) << @intCast(u6, line[i] - 65);
}
}
count += char_to_priority(@intCast(u8, 65 + 63) - @clz(parts[0] & parts[1] & parts[2]));
}
return .{ .int = count };
}
fn char_to_priority(char: u8) u8 {
if (char >= 65 and char <= 90)
return char - 38;
return char - 96;
}
|