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#include <algorithm>
#include <fstream>
#include <iostream>
#include <list>
#include <numeric>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
string
read_file(string_view filename)
{
fstream input{ filename };
return { istreambuf_iterator<char>{ input }, istreambuf_iterator<char>{} };
}
void
rtrim(string& str)
{
str.erase(find_if(str.rbegin(), str.rend(), [](auto chr) { return !isspace(chr); }).base(), str.end());
}
vector<string>
split(const string& line, char sep)
{
vector<string> parts{};
stringstream input{ line };
for ( string part; getline(input, part, sep); ) {
rtrim(part);
parts.emplace_back(part);
}
return parts;
}
unsigned int
calculate_hash(string_view str)
{
unsigned int value = 0;
for ( auto chr: str ) {
value += static_cast<unsigned char>(chr);
value *= 17;
}
return value % 256;
}
void
part1()
{
const auto parts = split(read_file("data/day15.txt"), ',');
cout << accumulate(parts.begin(), parts.end(), 0UL, [](auto init, const auto& str) { return init + calculate_hash(str); }) << endl;
}
void
part2()
{
vector<list<tuple<string, long>>> boxes(256);
const auto line = read_file("data/day15.txt");
const auto parts = split(line, ',');
for ( const auto& part: parts ) {
const auto pos = part.find_first_of("=-");
const auto lens = part.substr(0, pos);
auto& box = boxes[calculate_hash(lens)];
if ( part[pos] == '=' ) {
const auto value = stol(part.substr(pos + 1));
auto iter = find_if(box.begin(), box.end(), [&lens](const auto& element) { return get<0>(element) == lens; });
if ( iter == box.end() ) {
box.emplace_back(lens, value);
}
else {
*iter = { lens, value };
}
}
else {
box.remove_if([&lens](const auto& element) { return get<0>(element) == lens; });
}
}
long value = 0;
for ( size_t idx = 0; idx != boxes.size(); ++idx ) {
const auto& box = boxes[idx];
long lens_number = 1;
for ( const auto& lens: box ) {
value += static_cast<long>(idx + 1) * lens_number * get<1>(lens);
++lens_number;
}
}
cout << value << endl;
}
int
main()
{
part1();
part2();
}
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