80 lines
1.7 KiB
C++
80 lines
1.7 KiB
C++
#include <algorithm>
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#include <cstddef>
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#include <cstdint>
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#include <cstdlib>
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#include <iostream>
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#include <list>
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#include <string>
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#include <string_view>
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#include <utility>
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#include <vector>
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using UInt = std::uint64_t;
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using Lens = std::pair<std::string_view, UInt>;
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using LensList = std::list<Lens>;
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auto hash(std::string_view const str) -> std::uint8_t
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{
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std::uint8_t hash{0};
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for (auto const c : str) {
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hash += static_cast<std::uint8_t>(c);
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hash += hash << 4;
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}
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return hash;
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}
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auto main() -> int try {
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std::string line;
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std::vector<LensList> lenses(256);
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if (!std::getline(std::cin, line)) {
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std::cerr << "Unable to read input.";
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}
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for (std::ptrdiff_t pos{0}; pos < line.size(); ++pos) {
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auto const start{pos};
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while (line[pos] != '-' && line[pos] != '=') { ++pos; }
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std::string_view const id{line.begin() + start, line.begin() + pos};
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auto const h = hash(id);
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auto& box = lenses[h];
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auto it = std::ranges::find_if(box, [id](Lens const& l) {
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return l.first == id;
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});
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if (line[pos] == '-') {
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if (it != box.end()) {
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box.erase(it);
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}
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++pos;
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}
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else if (line[pos] == '=') {
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if (it != box.end()) {
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it->second = line[pos + 1] - '0';
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}
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else {
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box.emplace_back(id, line[pos + 1] - '0');
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}
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pos += 2;
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}
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else { std::abort(); }
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}
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UInt total{0};
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UInt box_id{1};
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for (auto const& box : lenses) {
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UInt lens_id{1};
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for (auto const [id, focal_length] : box) {
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total += box_id * lens_id * focal_length;
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++lens_id;
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}
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++box_id;
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}
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std::cout << "Total: " << total << '\n';
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return EXIT_SUCCESS;
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}
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catch (...) {
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std::cerr << "Uncaught exception.\n";
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return EXIT_FAILURE;
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}
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