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
|
#include "aoc.h"
#include <algorithm>
#include <vector>
namespace aoc2021 {
int decimal(const char* p) {
int d{0};
while (*p == '0' || *p == '1') {
d = 2 * d + *p - '0';
p++;
}
return d;
}
std::vector<line_view> filter(const std::vector<line_view>& vs, int i, char c) {
if (vs.size() == 1) {
return vs;
}
std::vector<line_view> n;
for (auto& lv : vs) {
if (*(lv.line + i) == c) {
n.push_back(lv);
}
}
return n;
}
void count(const std::vector<line_view>& v, int i, size_t* t0, size_t* t1) {
for (auto& l : v) {
if (*(l.line + i) == '1') {
(*t1)++;
} else {
(*t0)++;
}
}
}
char most_common(const std::vector<line_view>& v, int i, char x) {
size_t t0{0};
size_t t1{0};
count(v, i, &t0, &t1);
return t1 > t0 ? '1' : (t1 < t0 ? '0' : x);
}
char least_common(std::vector<line_view>& v, int i, char x) {
size_t t0{0};
size_t t1{0};
count(v, i, &t0, &t1);
return t1 > t0 ? '0' : (t1 < t0 ? '1' : x);
}
void filter(std::vector<line_view>& v1, std::vector<line_view>& v2, int i) {
if (i < 12) {
char c1 = most_common(v1, i, '1');
char c2 = least_common(v2, i, '0');
v1 = filter(v1, i, c1);
v2 = filter(v2, i, c2);
filter(v1, v2, i + 1);
}
}
std::pair<int, int> day3(line_view file) {
char gamma[13] = {0};
char epsilon[13] = {0};
int is[12] = {0};
int total{0};
std::vector<line_view> vs;
per_line(file, [&is, &total, &vs](line_view lv) {
vs.push_back(lv);
for (int i = 0; i < 12; i++) {
if (*(lv.line + i) == '1') {
is[i] += 1;
}
}
total += 1;
return true;
});
for (int i = 0; i < 12; i++) {
if (is[i] > total / 2) {
gamma[i] = '1';
epsilon[i] = '0';
} else {
gamma[i] = '0';
epsilon[i] = '1';
}
}
auto v1{vs};
auto v2{vs};
filter(v1, v2, 0);
int p1 = decimal(gamma) * decimal(epsilon);
int p2 = decimal(v1[0].line) * decimal(v2[0].line);
return {p1, p2};
}
} // namespace aoc2021
|
