90 lines
2.4 KiB
C++
90 lines
2.4 KiB
C++
#include <cassert>
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#include <cctype>
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#include <cstdint>
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#include <cstdlib>
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#include <iostream>
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#include <map>
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#include <string>
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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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struct Grid
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{
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void push(std::string const& s)
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{
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if (grid_.empty()) {
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grid_.emplace_back(s.length() + 2, '.');
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grid_.emplace_back(s.length() + 2, '.');
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}
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assert(s.length() + 2 == grid_.front().length());
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grid_.emplace(grid_.end() - 1, std::string(".") + s + std::string("."));
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}
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[[nodiscard]] auto loc(std::size_t const y, std::size_t const x) const -> UInt
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{
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return y * grid_.front().size() + x;
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}
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[[nodiscard]] auto sum_parts() const -> UInt
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{
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std::map<UInt, std::vector<UInt>> parts;
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for (std::size_t y{1}; y < grid_.size(); ++y) {
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for (auto x{1}; x < grid_[y].size(); ++x) {
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if (std::isdigit(grid_[y][x]) != 0) {
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std::vector<UInt> stars;
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UInt value = 0;
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if (grid_[y - 1][x - 1] == '*') { stars.emplace_back(loc(y - 1, x - 1)); }
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if (grid_[y][x - 1] == '*') { stars.emplace_back(loc(y, x - 1)); }
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if (grid_[y + 1][x - 1] == '*') { stars.emplace_back(loc(y + 1, x - 1)); }
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while (std::isdigit(grid_[y][x]) != 0) {
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value *= 10;
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value += grid_[y][x] - '0';
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if (grid_[y - 1][x] == '*') { stars.emplace_back(loc(y - 1, x)); }
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if (grid_[y + 1][x] == '*') { stars.emplace_back(loc(y + 1, x)); }
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++x;
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}
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if (grid_[y - 1][x] == '*') { stars.emplace_back(loc(y - 1, x)); }
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if (grid_[y][x] == '*') { stars.emplace_back(loc(y, x)); }
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if (grid_[y + 1][x] == '*') { stars.emplace_back(loc(y + 1, x)); }
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for (auto star : stars) {
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auto [it, inserted] = parts.insert(std::make_pair(star, std::vector<UInt>()));
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it->second.push_back(value);
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}
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}
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}
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}
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UInt sum{0};
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for (auto const& [id, sums] : parts) {
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if (sums.size() == 2) {
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sum += sums[0] * sums[1];
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}
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}
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return sum;
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}
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std::vector<std::string> grid_;
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};
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auto main() -> int try {
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Grid grid;
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std::string line;
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while (std::getline(std::cin, line)) {
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grid.push(line);
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}
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std::cout << "Part sum: " << grid.sum_parts() << '\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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