86 lines
2.0 KiB
C++
86 lines
2.0 KiB
C++
#include <cstdint>
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#include <iostream>
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#include <optional>
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#include <set>
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#include <sstream>
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#include <tuple>
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#include <vector>
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#include <doctest.h>
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#include <aocpp/Coord.hpp>
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#include <aocpp/Grid.hpp>
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#include <aocpp/Startup.hpp>
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using aocpp::Coord;
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using aocpp::Grid;
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namespace {
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auto Parse(std::istream & in) -> std::tuple<Coord, std::vector<Coord>, Coord, Grid>
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{
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Coord start1 {};
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std::vector<Coord> starts2;
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Coord end {};
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auto grid = Grid::Parse(in);
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grid.each([&](Coord c, char v) {
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switch (v) {
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case 'S': grid[c] = 'a'; start1 = c; break;
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case 'E': grid[c] = 'z'; end = c; break;
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case 'a': starts2.push_back(c); break;
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}
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});
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return {start1, std::move(starts2), end, std::move(grid)};
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}
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auto Solve(std::vector<Coord> starts, Coord end, Grid const& grid) -> std::optional<std::int64_t>
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{
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std::vector<Coord> next_layer;
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std::set<Coord> seen;
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std::int64_t counter {1};
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while (!starts.empty()) {
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for (auto here : starts) {
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if (!seen.insert(here).second) continue;
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auto here_height = grid[here];
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for (auto next : {Up(here), Down(here), Left(here), Right(here)}) {
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if (!grid.contains(next)) continue;
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if (grid[next] - 1 > here_height) continue;
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if (next == end) { return counter; }
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next_layer.push_back(next);
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}
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}
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counter++;
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starts.clear();
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std::swap(starts, next_layer);
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}
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return {};
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}
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} // namespace
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TEST_SUITE("2022-12 examples") {
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TEST_CASE("documented example") {
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std::istringstream in {
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"Sabqponm\n"
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"abcryxxl\n"
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"accszExk\n"
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"acctuvwj\n"
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"abdefghi\n"
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};
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auto [start1, starts2, end, grid] = Parse(in);
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CHECK(31 == Solve({start1}, end, grid));
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CHECK(29 == Solve(std::move(starts2), end, grid));
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}
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}
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auto Main(std::istream & in, std::ostream & out) -> void
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{
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auto [start1, starts2, end, grid] = Parse(in);
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out << "Part 1: " << Solve({start1}, end, grid).value_or(-1) << std::endl;
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out << "Part 2: " << Solve(std::move(starts2), end, grid).value_or(-1) << std::endl;
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}
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