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
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
|
const std = @import("std");
const example = @embedFile("example");
const input = @embedFile("input");
var allocator: std.mem.Allocator = undefined;
pub fn main() anyerror!void {
var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
defer arena.deinit();
allocator = arena.allocator();
try std.testing.expectEqual(try solve(example), 13);
const result = try solve(input);
try std.io.getStdOut().writer().print("{}\n", .{result});
}
const ListErrors = error{
OutOfMemory,
};
const List = struct {
data: std.ArrayList(Elt),
fn init(reader: anytype) !*List {
var l = try allocator.create(List);
l.data = std.ArrayList(Elt).init(allocator);
while (true) {
const c = reader.readByte() catch break;
switch (c) {
'[' => {
var e = try l.data.addOne();
e.* = Elt{ .list = try List.init(reader) };
},
']' => {
return l;
},
',' => { // comma after a list ending, ignore
},
else => { // a digit
var e = try l.data.addOne();
e.* = Elt{ .int = c - '0' };
while (true) {
const d = reader.readByte() catch unreachable;
if (d == ']') {
return l;
} else if (d == ',') {
break;
}
e.int = e.int * 10 + d;
}
},
}
}
return l;
}
fn initSingleton(n: u8) !*List {
var l = try allocator.create(List);
l.data = std.ArrayList(Elt).init(allocator);
var e = try l.data.addOne();
e.* = Elt{ .int = n };
return l;
}
fn isLowerThan(l: *List, o: *List) ListErrors!?bool {
var i: usize = 0;
while (true) : (i += 1) {
if (o.len() <= i) {
if (l.len() <= i) {
return null;
}
return false;
}
if (l.len() <= i) {
return true;
}
const t = try l.data.items[i].isLowerThan(&(o.data.items[i]));
if (t != null) {
return t;
}
}
}
inline fn len(l: *List) usize {
return l.data.items.len;
}
fn print(l: *List) void {
for (l.data.items) |e| {
switch (e) {
Elt.int => |i| std.debug.print("{d} ", .{i}),
Elt.list => |o| {
std.debug.print("[", .{});
o.print();
std.debug.print("]", .{});
},
}
}
}
};
const EltType = enum {
int,
list,
};
const Elt = union(EltType) {
int: u8,
list: *List,
fn isLowerThan(e: *Elt, f: *Elt) !?bool {
switch (e.*) {
Elt.int => |i| switch (f.*) {
Elt.int => |j| {
if (i == j) {
return null;
}
return i < j;
},
Elt.list => |o| {
var l = try List.initSingleton(i);
return l.isLowerThan(o);
},
},
Elt.list => |l| switch (f.*) {
Elt.int => |j| {
f.* = Elt{ .list = try List.initSingleton(j) };
return e.isLowerThan(f);
},
Elt.list => |o| {
return l.isLowerThan(o);
},
},
}
}
};
fn solve(puzzle: []const u8) !u64 {
var it = std.mem.tokenize(u8, puzzle, "\n");
var i: usize = 1;
var tot: usize = 0;
while (it.next()) |line| {
var firstLine = std.io.fixedBufferStream(line);
var first = try List.init(firstLine.reader());
var secondLine = std.io.fixedBufferStream(it.next() orelse unreachable);
var second = try List.init(secondLine.reader());
const t = try first.isLowerThan(second);
//first.print();
//std.debug.print("\n", .{});
//second.print();
//std.debug.print("\n{d}: {?}\n", .{ i, t });
if (t) |s| {
if (s) {
tot += i;
}
}
i += 1;
}
return tot;
}
|
