blob: 49a9ec19a994345e04020f269f43b814a516fb78 (
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
|
#include <algorithm>
#include <filesystem>
#include <fstream>
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
namespace {
struct Range {
long long start;
long long end;
};
vector<Range>
readFile(const filesystem::path& filename)
{
ifstream file{ filename };
vector<Range> ranges;
for ( string line; getline(file, line); ) {
stringstream stream{ line };
char dash{};
long long start{};
long long end{};
stream >> start >> dash >> end;
ranges.emplace_back(start, end);
}
return ranges;
}
void
sortRanges(vector<Range>& ranges)
{
ranges::sort(ranges, [](const auto& lhs, const auto& rhs) {
if ( lhs.start != rhs.start ) {
return lhs.start < rhs.start;
}
return lhs.end < rhs.end;
});
}
void
mergeRanges(vector<Range>& ranges)
{
if ( ranges.empty() ) {
return;
}
vector<Range> mergedRanges;
auto current = ranges[0];
for ( size_t i = 1; i != ranges.size(); ++i ) {
if ( ranges[i].start <= current.end + 1 ) {
current.end = max(current.end, ranges[i].end);
}
else {
mergedRanges.emplace_back(current);
current = ranges[i];
}
}
mergedRanges.emplace_back(current);
ranges.swap(mergedRanges);
}
long long
findLowestAllowedIP(const vector<Range>& ranges)
{
if ( ranges.empty() || ranges[0].start > 0 ) {
return 0;
}
return ranges[0].end + 1;
}
long long
countAllowedIPs(const vector<Range>& ranges, long long max_ip)
{
long long allowed_count = 0;
for ( size_t i = 0; i < ranges.size() - 1; ++i ) {
allowed_count += ranges[i + 1].start - ranges[i].end - 1;
}
if ( !ranges.empty() && ranges.back().end < max_ip ) {
allowed_count += max_ip - ranges.back().end;
}
if ( ranges.empty() ) {
allowed_count = max_ip + 1;
}
return allowed_count;
}
void
part1(vector<Range> ranges)
{
sortRanges(ranges);
mergeRanges(ranges);
cout << findLowestAllowedIP(ranges) << '\n';
}
void
part2(vector<Range> ranges, long long max_ip = 4294967295)
{
sortRanges(ranges);
mergeRanges(ranges);
cout << countAllowedIPs(ranges, max_ip) << '\n';
}
} // namespace
int
main()
{
auto ranges = readFile("data/day20.txt");
part1(ranges);
part2(ranges);
}
|
