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
|
#include <array>
#include <chrono>
#include <fstream>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <vector>
using namespace std;
vector<string>
read_file(string_view filename)
{
fstream input{ filename };
vector<string> data;
for ( string line; getline(input, line); ) {
data.emplace_back(line);
}
return data;
}
const unsigned DIR_UP = 0;
const unsigned DIR_RIGHT = 1;
const unsigned DIR_DOWN = 2;
const unsigned DIR_LEFT = 3;
size_t
solve(const vector<string>& lines, tuple<size_t, size_t, unsigned int> start)
{
static const array<tuple<size_t, size_t>, 4> movement{
make_tuple(0, -1),
make_tuple(1, 0),
make_tuple(0, 1),
make_tuple(-1, 0),
};
map<tuple<size_t, size_t, unsigned int>, bool> visited;
queue<tuple<size_t, size_t, unsigned int>> positions;
positions.emplace(start);
while ( !positions.empty() ) {
auto row = get<0>(positions.front());
auto col = get<1>(positions.front());
auto dir = get<2>(positions.front());
positions.pop();
while ( true ) {
col += get<0>(movement[dir]); // NOLINT
row += get<1>(movement[dir]); // NOLINT
if ( row >= lines.size() || col >= lines[0].size() ) {
break;
}
if ( visited[{ row, col, dir }] ) {
break;
}
visited[{ row, col, dir }] = true;
const auto chr = lines[row][col];
if ( chr == '|' && (dir == DIR_LEFT || dir == DIR_RIGHT) ) {
dir = (dir + 1) % 4;
positions.emplace(row, col, (dir + 2) % 4);
}
else if ( chr == '-' && (dir == DIR_UP || dir == DIR_DOWN) ) {
dir = (dir + 1) % 4;
positions.emplace(row, col, (dir + 2) % 4);
}
else if ( chr == '/' && (dir == DIR_LEFT || dir == DIR_RIGHT) ) {
dir = (dir + 3) % 4;
}
else if ( chr == '/' && (dir == DIR_UP || dir == DIR_DOWN) ) {
dir = (dir + 1) % 4;
}
else if ( chr == '\\' && (dir == DIR_LEFT || dir == DIR_RIGHT) ) {
dir = (dir + 1) % 4;
}
else if ( chr == '\\' && (dir == DIR_UP || dir == DIR_DOWN) ) {
dir = (dir + 3) % 4;
}
}
}
set<tuple<size_t, size_t>> foo;
for (const auto& bar: visited) {
foo.emplace(get<0>(bar.first), get<1>(bar.first));
}
return foo.size();
}
void
part1(const vector<string>& lines)
{
auto start = chrono::steady_clock::now();
auto sum = solve(lines, { 0, -1, DIR_RIGHT });
auto duration = chrono::duration_cast<chrono::milliseconds>(chrono::steady_clock::now() - start).count();
cout << sum << " (" << duration << "ms)" << endl;
}
void
part2(const vector<string>& lines)
{
const auto rows = lines.size();
const auto cols = lines[0].size();
auto start = chrono::steady_clock::now();
size_t sum = 0;
for ( size_t row = 0; row != rows; ++row ) {
sum = max(sum, solve(lines, { row, -1, DIR_RIGHT }));
sum = max(sum, solve(lines, { row, cols, DIR_LEFT }));
}
for ( size_t col = 0; col != cols; ++col ) {
sum = max(sum, solve(lines, { -1, col, DIR_DOWN }));
sum = max(sum, solve(lines, { rows, col, DIR_UP }));
}
auto duration = chrono::duration_cast<chrono::milliseconds>(chrono::steady_clock::now() - start).count();
cout << sum << " (" << duration << "ms)" << endl;
}
int
main()
{
const auto lines = read_file("data/day16.txt");
part1(lines);
part2(lines);
}
|
