96 lines
2.2 KiB
C++
96 lines
2.2 KiB
C++
#include <algorithm>
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#include <deque>
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#include <iostream>
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#include <map>
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#include <tuple>
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#include <utility>
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#include <vector>
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#include <intcode/intcode.hpp>
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#include <intcode/Coord.hpp>
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using namespace intcode;
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namespace {
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using CoordOp = Coord(Coord);
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CoordOp* const moves[4] {Up, Down, Left, Right};
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auto Interact(Machine & m, ValueType cmd) -> ValueType {
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StepInput(m, cmd);
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return StepOutput(m);
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}
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auto CounterCommand(ValueType x) -> ValueType {
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return ((x-1)^1)+1;
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}
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// Depth first search of the maze
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auto Explore(Machine m) -> std::map<Coord, ValueType> {
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std::map<Coord, ValueType> world;
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std::vector<ValueType> path {0};
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Coord here {};
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for(;;) {
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while (path.back() < 4) {
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path.back()++;
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auto here_ = moves[path.back() - 1](here);
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auto [it, success] = world.insert({here_,0});
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if (success && 0 != (it->second = Interact(m, path.back()))) {
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here = here_;
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path.push_back(0);
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}
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}
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path.pop_back();
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if (path.empty()) { break; }
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auto rev = CounterCommand(path.back());
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here = moves[rev - 1](here);
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Interact(m, rev);
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}
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return world;
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}
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// Breadth first search of maze finding shortest path to origin
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// and furthest point in the maze from the airsource.
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auto Compute(std::map<Coord, ValueType> world) -> std::pair<int, int> {
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// Find starting coordinate and remove all the walls from the map
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Coord start {};
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for (auto it = world.begin(); it != world.end(); ) {
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switch (it->second) {
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case 2: start = it->first;
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case 0: it = world.erase(it); break;
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default: it++;
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}
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}
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int part1 = -1;
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int part2 = -1;
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for (std::deque<std::pair<int, Coord>> todo {{0,start}};
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!todo.empty();
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todo.pop_front())
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{
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auto [steps, here] = todo.front();
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if (Coord{0,0} == here) part1 = steps;
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part2 = steps;
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for (auto fn : moves) {
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auto next = fn(here);
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if (world.erase(next)) {
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todo.emplace_back(steps+1, next);
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}
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}
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}
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return {part1, part2};
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}
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} // namespace
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auto main() -> int {
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auto [p1,p2] = Compute(Explore(Machine{ParseStream(std::cin)}));
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std::cout << "Part 1: " << p1 << std::endl;
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std::cout << "Part 2: " << p2 << std::endl;
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}
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