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advent-of-code/2021/puzzle-23-02.cc
Matthew Gretton-Dann 29005ed7ba Improved version of 2021 puzzle 23-02
Building on changes to part 1 see if this performs better and produces correct results.
2021-12-25 08:58:21 +00:00

343 lines
10 KiB
C++

#include <array>
#include <cassert>
#include <functional>
#include <iostream>
#include <map>
#include <regex>
#include <set>
#include <string>
// Map:
// #############
// #ab.c.d.e.fg#
// ###h#i#j#k###
// #l#m#n#o#
// #########
//
// 0 -1- 1 -2- 2 -2- 3 -2- 4 -2- 5 -1- 6
// \ / \ / \ / \ /
// 2 2 2 2 2 2 2 2
// + + + +
// 7 8 9 10
// | | | |
// 1 1 1 1
// | | | |
// 11 12 13 14
// | | | |
// 1 1 1 1
// | | | |
// 15 16 17 18
// | | | |
// 1 1 1 1
// | | | |
// 19 20 21 22
// Actually : {0-6} can go to any of {7-10} at varying cost but there are move restritions.
using Position = char;
using UInt = int;
using Type = char;
std::multimap<Position, std::pair<Position, UInt>> valid_moves{
{0, {7, 3}}, {0, {8, 5}}, {0, {9, 7}}, {0, {10, 9}}, {1, {7, 2}}, {1, {8, 4}},
{1, {9, 6}}, {1, {10, 8}}, {2, {7, 2}}, {2, {8, 2}}, {2, {9, 4}}, {2, {10, 6}},
{3, {7, 4}}, {3, {8, 2}}, {3, {9, 2}}, {3, {10, 4}}, {4, {7, 6}}, {4, {8, 4}},
{4, {9, 2}}, {4, {10, 2}}, {5, {7, 8}}, {5, {8, 6}}, {5, {9, 4}}, {5, {10, 2}},
{6, {7, 9}}, {6, {8, 7}}, {6, {9, 5}}, {6, {10, 3}}, {7, {0, 3}}, {7, {1, 2}},
{7, {2, 2}}, {7, {3, 4}}, {7, {4, 6}}, {7, {5, 8}}, {7, {6, 9}}, {7, {11, 1}},
{8, {0, 5}}, {8, {1, 4}}, {8, {2, 2}}, {8, {3, 2}}, {8, {4, 4}}, {8, {5, 6}},
{8, {6, 7}}, {8, {12, 1}}, {9, {0, 7}}, {9, {1, 6}}, {9, {2, 4}}, {9, {3, 2}},
{9, {4, 2}}, {9, {5, 4}}, {9, {6, 5}}, {9, {13, 1}}, {10, {0, 9}}, {10, {1, 8}},
{10, {2, 6}}, {10, {3, 4}}, {10, {4, 2}}, {10, {5, 2}}, {10, {6, 3}}, {10, {14, 1}},
{11, {7, 1}}, {12, {8, 1}}, {13, {9, 1}}, {14, {10, 1}}, {11, {15, 1}}, {12, {16, 1}},
{13, {17, 1}}, {14, {18, 1}}, {15, {11, 1}}, {16, {12, 1}}, {17, {13, 1}}, {18, {14, 1}},
{14, {10, 1}}, {15, {19, 1}}, {16, {20, 1}}, {17, {21, 1}}, {18, {22, 1}}, {19, {15, 1}},
{20, {16, 1}}, {21, {17, 1}}, {22, {18, 1}}};
std::map<Type, UInt> multipliers{{'A', 1}, {'B', 10}, {'C', 100}, {'D', 1000}};
struct State
{
static constexpr UInt size_ = 23;
auto finished() const noexcept -> bool { return nodes_ == finished_; }
auto size() const noexcept -> UInt { return size_; }
auto node(unsigned idx) noexcept -> Type& { return nodes_[idx]; }
auto node(unsigned idx) const noexcept -> Type const& { return nodes_[idx]; }
auto cost() const noexcept -> UInt { return cost_; }
bool check_move(unsigned from, unsigned to)
{
if (nodes_[from] == '.' || nodes_[to] != '.') {
return false;
}
if (from > 18) {
// Only move out of the bottom row if we're not meant to be here.
return nodes_[from] != finished_[from];
}
if (from > 14 && from < 19) {
if (to < 15) {
// Second bottom row - only move up if we're not meant to be here or the one below isn't.
return nodes_[from] != finished_[from] ||
(nodes_[from + 4] != '.' && nodes_[from + 4] != finished_[from + 4]);
}
// Moving down - only do it if we're of the right type.
return nodes_[from] == finished_[to];
}
if (from > 10 && from < 15) {
// Second top row.
if (to < 11) {
return nodes_[from] != finished_[from] ||
(nodes_[from + 4] != '.' && nodes_[from + 4] != finished_[from + 4]) ||
(nodes_[from + 8] != '.' && nodes_[from + 8] != finished_[from + 8]);
}
// Moving down - only do it if we're of the right type.
return nodes_[from] == finished_[to];
}
if (from > 6 && from < 11) {
if (to > 10) {
// Only move into bottom position if we're moving the correct piece.
return nodes_[from] == finished_[to];
}
// Moving to top row
if (to == 0 && nodes_[1] != '.') {
return false;
}
if (to < 2 && from > 7 && nodes_[2] != '.') {
return false;
}
if (to < 3 && from > 8 && nodes_[3] != '.') {
return false;
}
if (to < 4 && from > 9 && nodes_[4] != '.') {
return false;
}
if (to == 6 && nodes_[5] != '.') {
return false;
}
if (to > 4 && from < 10 && nodes_[4] != '.') {
return false;
}
if (to > 3 && from < 9 && nodes_[3] != '.') {
return false;
}
if (to > 2 && from < 8 && nodes_[2] != '.') {
return false;
}
return true;
}
if (from < 7) {
// Can only move down if we're the right type.
if (nodes_[from] != finished_[to]) {
return false;
}
// Now encode the rules about moving along the top.
if (from == 0 && nodes_[1] != '.') {
return false;
}
if (from < 2 && to > 7 && nodes_[2] != '.') {
return false;
}
if (from < 3 && to > 8 && nodes_[3] != '.') {
return false;
}
if (from < 4 && to > 9 && nodes_[4] != '.') {
return false;
}
if (from == 6 && nodes_[5] != '.') {
return false;
}
if (from > 4 && to < 10 && nodes_[4] != '.') {
return false;
}
if (from > 3 && to < 9 && nodes_[3] != '.') {
return false;
}
if (from > 2 && to < 8 && nodes_[2] != '.') {
return false;
}
return true;
}
abort();
}
bool move(unsigned from, unsigned to, UInt cost)
{
if (!check_move(from, to)) {
return false;
}
std::swap(nodes_[from], nodes_[to]);
cost_ += cost;
return true;
}
bool operator<(State const& rhs) const noexcept { return nodes_ < rhs.nodes_; }
bool operator==(State const& rhs) const noexcept { return nodes_ < rhs.nodes_; }
private:
std::array<Type, size_> nodes_{'.'};
static std::array<Type, size_> finished_;
UInt cost_{0};
};
std::array<Type, State::size_> State::finished_ = {'.', '.', '.', '.', '.', '.', '.', 'A',
'B', 'C', 'D', 'A', 'B', 'C', 'D', 'A',
'B', 'C', 'D', 'A', 'B', 'C', 'D'};
struct StateCmp
{
bool operator()(State const* lhs, State const* rhs) const noexcept
{
if (lhs == nullptr && rhs != nullptr) {
return true;
}
if (rhs == nullptr) {
return true;
}
return *lhs < *rhs;
}
};
struct CostStateCmp
{
bool operator()(State const* lhs, State const* rhs) const noexcept
{
if (lhs == nullptr && rhs != nullptr) {
return true;
}
if (rhs == nullptr) {
return true;
}
return lhs->cost() < rhs->cost() || (lhs->cost() == rhs->cost() && *lhs < *rhs);
}
};
auto main() -> int
{
std::regex line2_re{R"(#(.)(.)\.(.)\.(.)\.(.)\.(.)(.)#)"};
std::regex line3_re{"###(.)#(.)#(.)#(.)###"};
std::regex line4_re{"#(.)#(.)#(.)#(.)#"};
std::string line;
std::smatch m;
std::getline(std::cin, line);
if (line != "#############") {
std::cerr << "Incorrect first line.\n";
return 1;
}
State* initial_state = new State;
std::getline(std::cin, line);
if (!std::regex_search(line, m, line2_re)) {
std::cerr << "Unable to match line 2 " << line << '\n';
return 1;
}
for (unsigned i = 0; i < 7; ++i) {
initial_state->node(i) = m.str(i + 1)[0];
}
std::getline(std::cin, line);
if (!std::regex_search(line, m, line3_re)) {
std::cerr << "Unable to match line 3 " << line << '\n';
return 1;
}
for (unsigned i = 0; i < 4; ++i) {
initial_state->node(7 + i) = m.str(i + 1)[0];
}
std::getline(std::cin, line);
if (!std::regex_search(line, m, line4_re)) {
std::cerr << "Unable to match line 4 " << line << '\n';
return 1;
}
for (unsigned i = 0; i < 4; ++i) {
initial_state->node(11 + i) = m.str(i + 1)[0];
}
std::getline(std::cin, line);
if (!std::regex_search(line, m, line4_re)) {
std::cerr << "Unable to match line 5 " << line << '\n';
return 1;
}
for (unsigned i = 0; i < 4; ++i) {
initial_state->node(15 + i) = m.str(i + 1)[0];
}
std::getline(std::cin, line);
if (!std::regex_search(line, m, line4_re)) {
std::cerr << "Unable to match line 6 " << line << '\n';
return 1;
}
for (unsigned i = 0; i < 4; ++i) {
initial_state->node(19 + i) = m.str(i + 1)[0];
}
std::set<State*, StateCmp> states;
std::set<State*, CostStateCmp> costs;
std::set<State*, StateCmp> visited;
states.insert(initial_state);
costs.insert(initial_state);
while (!costs.empty()) {
assert(costs.size() == states.size());
auto it{costs.begin()};
State* state{*it};
visited.insert(state);
states.erase(state);
costs.erase(it);
if (visited.size() % 10'000 == 0) {
std::cout << "Visited: " << visited.size() << " number of states: " << states.size()
<< " Min energy: " << state->cost() << '\n';
}
if (state->finished()) {
std::cout << "Done with cost " << state->cost() << '\n';
return 0;
}
for (unsigned i = 0; i < state->size(); ++i) {
if (state->node(i) == '.') {
continue;
}
auto [it_begin, it_end] = valid_moves.equal_range(i);
for (auto move_it{it_begin}; move_it != it_end; ++move_it) {
State* next_state = new State{*state};
UInt cost_delta = move_it->second.second * multipliers[state->node(i)];
bool keep{false};
if (next_state->move(i, move_it->second.first, cost_delta) &&
!visited.contains(next_state)) {
auto [insert_it, success] = states.insert(next_state);
if (!success) {
auto old_state{*insert_it};
if (next_state->cost() < old_state->cost()) {
keep = true;
costs.erase(old_state);
states.erase(old_state);
states.insert(next_state);
costs.insert(next_state);
}
}
else {
keep = true;
costs.insert(next_state);
}
}
if (!keep) {
delete next_state;
}
}
}
}
std::cerr << "FAILED\n";
return 1;
}