blob: b9d6355b0ce54ccc3f712151179610e847cafd83 (
plain)
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
|
#include <fstream>
#include <iostream>
#include <sstream>
#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;
}
void
part1()
{
typedef tuple<size_t, size_t> pos_t;
const auto puzzle = read_file("data/day10.txt");
const auto find_start_pos = [&]() -> pos_t {
for ( size_t y = 0; y != puzzle.size(); ++y ) { // NOLINT
auto x = puzzle[y].find('S'); // NOLINT
if ( x != string::npos ) {
return { x, y };
}
}
return { 0, 0 };
};
const auto predict_direction = [&](pos_t& current, char& direction) -> bool {
auto x = get<0>(current); // NOLINT
auto y = get<1>(current); // NOLINT
if ( direction == 'S' ) {
++y;
if ( y >= puzzle.size() ) {
return false;
}
auto tile = puzzle[y][x];
if ( tile != 'J' && tile != '|' && tile != 'L' ) {
return false;
}
if ( tile == 'J' ) {
direction = 'W';
}
else if ( tile == 'L' ) {
direction = 'E';
}
}
else if ( direction == 'N' ) {
--y;
if ( y >= puzzle.size() ) {
return false;
}
auto tile = puzzle[y][x];
if ( tile != '7' && tile != '|' && tile != 'F' ) {
return false;
}
if ( tile == '7' ) {
direction = 'W';
}
else if ( tile == 'F' ) {
direction = 'E';
}
}
else if ( direction == 'E' ) {
++x;
if ( x >= puzzle[y].size() ) {
return false;
}
auto tile = puzzle[y][x];
if ( tile != 'J' && tile != '-' && tile != '7' ) {
return false;
}
if ( tile == 'J' ) {
direction = 'N';
}
else if ( tile == '7' ) {
direction = 'S';
}
}
else if ( direction == 'W' ) {
--x;
if ( x >= puzzle[y].size() ) {
return false;
}
auto tile = puzzle[y][x];
if ( tile != 'L' && tile != '-' && tile != 'F' ) {
return false;
}
if ( tile == 'L' ) {
direction = 'N';
}
else if ( tile == 'F' ) {
direction = 'S';
}
}
else {
cerr << "invalid direction " << direction << ")!" << endl;
return false;
}
current = { x, y };
return true;
};
const auto start_pos = find_start_pos();
auto max_steps = 0;
for ( const auto direction: { 'N', 'S', 'E', 'W' } ) {
auto current_direction = direction;
auto current_pos = start_pos;
auto steps = 0;
for ( ;; ) {
++steps;
if ( !predict_direction(current_pos, current_direction) ) {
break;
}
}
cout << "Richtung: " << direction << " - Schritte: " << steps << endl;
max_steps = max(max_steps, steps);
}
cout << max_steps / 2 << endl;
}
int
main()
{
part1();
}
|
