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const std = @import("std");
const test_input =
\\L68
\\L30
\\R48
\\L5
\\R60
\\L55
\\L1
\\L99
\\R14
\\L82
;
test part1 {
var arena = std.heap.ArenaAllocator.init(std.testing.allocator);
defer arena.deinit();
const allocator = arena.allocator();
try std.testing.expectEqual(3, try part1(allocator, try parse(allocator, test_input)));
}
test part2 {
var arena = std.heap.ArenaAllocator.init(std.testing.allocator);
defer arena.deinit();
const allocator = arena.allocator();
try std.testing.expectEqual(6, try part2(allocator, try parse(allocator, test_input)));
}
test "part2 a" {
var arena = std.heap.ArenaAllocator.init(std.testing.allocator);
defer arena.deinit();
const allocator = arena.allocator();
try std.testing.expectEqual(1, try part2(allocator, try parse(allocator,
\\L50
)));
}
const Direction = enum { left, right };
const Input = []struct {
direction: Direction,
amount: u32,
};
pub fn parse(allocator: std.mem.Allocator, input: []const u8) !Input {
var lines = std.mem.splitScalar(u8, input, '\n');
var rotations = try std.ArrayList(@typeInfo(Input).pointer.child).initCapacity(allocator, 0);
while (lines.next()) |line| {
if (line.len == 0) continue;
const direction: Direction = switch (line[0]) {
'L' => .left,
'R' => .right,
else => return error.InvalidDirection,
};
const amount = try std.fmt.parseInt(u32, line[1..], 10);
try rotations.append(allocator, .{ .direction = direction, .amount = amount });
}
return rotations.toOwnedSlice(allocator);
}
pub fn part1(_: std.mem.Allocator, input: Input) !u32 {
var dial: i32 = 50;
var password: u32 = 0;
for (input) |rotation| {
dial += switch (rotation.direction) {
.left => -@as(i32, @intCast(rotation.amount)),
.right => @intCast(rotation.amount),
};
dial = @mod(dial, 100);
if (dial == 0) password += 1;
}
return password;
}
pub fn part2(_: std.mem.Allocator, input: Input) !u32 {
var dial: i32 = 50;
var password: u32 = 0;
for (input) |rotation| {
// Smoothbrain solution right here
for (0..rotation.amount) |_| {
dial += switch (rotation.direction) { .left => -1, .right => 1 };
dial = @mod(dial, 100);
if (dial == 0) password += 1;
}
}
return password;
}
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