86 lines
3.0 KiB
C++
86 lines
3.0 KiB
C++
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#include <fstream>
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#include <iostream>
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#include <sstream>
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#include <vector>
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#include <unordered_set>
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using Rucksack = std::pair<std::unordered_set<char>, std::unordered_set<char>>;
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std::vector<Rucksack> getRucksacks( std::ifstream &file ) {
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std::vector<Rucksack> ret{};
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std::string str;
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while ( std::getline( file, str ) ) {
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ret.emplace_back();
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for(size_t i = 0; i < str.length()/2; i++) {
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ret.back().first.emplace(str[i]);
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}
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for(size_t i = str.length()/2; i < str.length(); i++) {
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ret.back().second.emplace(str[i]);
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}
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}
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return ret;
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}
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size_t getItemPriority(char item) {
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if(item <= 'Z') {
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return item - 'A' + 27;
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}
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return item - 'a' + 1;
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}
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size_t getPriorityPart1(const std::vector<Rucksack> &rucksacks) {
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size_t res = 0;
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for(auto &rucksack : rucksacks) {
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for(auto &item : rucksack.first) {
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if(rucksack.second.find(item) != rucksack.second.end()) {
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res += getItemPriority(item);
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break;
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}
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}
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}
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return res;
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}
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void findItemsInCommon(const std::unordered_set<char> &a, const std::unordered_set<char> &b, std::unordered_set<char> &result) {
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for(auto &item : a) {
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if(b.find(item) != b.end()) {
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result.emplace(item);
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}
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}
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}
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size_t getPriorityPart2(const std::vector<Rucksack> &rucksacks) {
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size_t res = 0;
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for(size_t group = 0; group < rucksacks.size(); group += 3) {
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std::unordered_set<char> possibilities{};
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findItemsInCommon(rucksacks[group].first, rucksacks[group+1].first, possibilities);
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findItemsInCommon(rucksacks[group].first, rucksacks[group+1].second, possibilities);
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findItemsInCommon(rucksacks[group].second, rucksacks[group+1].first, possibilities);
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findItemsInCommon(rucksacks[group].second, rucksacks[group+1].second, possibilities);
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std::unordered_set<char> result{};
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findItemsInCommon(rucksacks[group+2].first, possibilities, result);
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findItemsInCommon(rucksacks[group+2].first, possibilities, result);
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findItemsInCommon(rucksacks[group+2].second, possibilities, result);
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findItemsInCommon(rucksacks[group+2].second, possibilities, result);
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if(result.size() != 1) {
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std::cerr << "Something strange is afoot!" << std::endl;
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for(auto &item : result) {
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std::cerr << item << std::endl;
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}
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exit(1);
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}
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res += getItemPriority(*result.begin());
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}
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return res;
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}
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int main() {
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std::ifstream input_file( "input" );
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auto rucksacks = getRucksacks( input_file );
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int part1 = getPriorityPart1(rucksacks);
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std::cout << "Priority of item types that are in both compartmens is \033[91;1m" << part1
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<< "\033[0m." << std::endl;
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int part2 = getPriorityPart2(rucksacks);
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std::cout << "Priority of all Elf groups is \033[91;1m" << part2
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<< "\033[0m." << std::endl;
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}
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