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#include <algorithm>
#include <fstream>
#include <iostream>
#include <iterator>
#include <map>
#include <set>
#include <string>
#include <vector>
using namespace std;
set<char>
make_unique(string_view str)
{
return { begin(str), end(str) };
}
map<char, int>
make_lookup()
{
map<char, int> lookup;
for ( int i = 0; i != 26; ++i ) {
lookup[char('a' + i)] = i + 1;
lookup[char('A' + i)] = i + 27;
}
return lookup;
}
vector<tuple<set<char>, set<char>>>
read_file(string_view filename)
{
fstream input{ filename };
vector<tuple<set<char>, set<char>>> data;
for ( string line; getline(input, line); ) {
const auto lhs = line.substr(0, line.length() / 2);
const auto rhs = line.substr(line.length() / 2);
data.emplace_back(make_unique(lhs), make_unique(rhs));
}
return data;
}
vector<string>
read_file2(string_view filename)
{
fstream input{ filename };
vector<string> data;
for ( string line; getline(input, line); ) {
data.emplace_back(line);
}
return data;
}
void
part1(const vector<tuple<set<char>, set<char>>>& data)
{
auto lookup = make_lookup();
int sum = 0;
for ( const auto& [lhs, rhs]: data ) {
string intersection;
set_intersection(begin(lhs), end(lhs), begin(rhs), end(rhs), back_inserter(intersection));
sum += lookup[intersection[0]];
}
cout << sum << endl;
}
void
part2(const vector<string>& data)
{
auto lookup = make_lookup();
int sum = 0;
for ( size_t i = 0; i < data.size(); i += 3 ) {
map<char, int> count;
const array<set<char>, 3> sets = { make_unique(data[i]),
make_unique(data[i + 1]),
make_unique(data[i + 2]) };
for ( const auto& set: sets ) {
for ( const auto chr: set ) {
count[chr]++;
}
}
for ( const auto& [key, value]: count ) {
if ( value == 3 ) {
sum += lookup[key];
}
}
}
cout << sum << endl;
}
int
main()
{
const auto* const filename = "data/day03.txt";
part1(read_file(filename));
part2(read_file2(filename));
}
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