mgrettondann/advent-of-code
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Proposed solutions for 2021 day 23

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Improve speed by using two sets for State management:

states: Contains all the states we need to visit indexed by state - Cost is ignored.
costs:  Contains all the states we need to visit indexed by cost then state.

This then means the lookup for the minimum cost is fast.
This commit is contained in:
Matthew Gretton-Dann
2021-12-24 11:53:57 +00:00
parent b53002d48a
commit cca3a22a43
1 changed files with 88 additions and 58 deletions
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146
2021/puzzle-23-01.cc
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@@ -1,12 +1,11 @@
#include <array>
#include <cassert>
#include <functional>
#include <iostream>
#include <map>
#include <regex>
#include <set>
#include <string>
#include <unordered_map>
#include <unordered_set>
// Map:
// #############
@@ -29,15 +28,13 @@ using Position = char;
using UInt = int;
using Type = char;
std::multimap<Position, std::pair<Position, UInt>> costs{
{'a', {'b', 1}}, {'b', {'a', 1}}, {'b', {'c', 2}}, {'b', {'h', 2}}, {'c', {'b', 2}},
{'c', {'d', 2}}, {'c', {'h', 2}}, {'c', {'i', 2}}, {'d', {'c', 2}}, {'d', {'e', 2}},
{'d', {'i', 2}}, {'d', {'j', 2}}, {'e', {'d', 2}}, {'e', {'f', 2}}, {'e', {'j', 2}},
{'e', {'k', 2}}, {'f', {'e', 2}}, {'f', {'g', 1}}, {'f', {'k', 2}}, {'g', {'f', 1}},
{'h', {'b', 2}}, {'h', {'c', 2}}, {'h', {'l', 1}}, {'i', {'c', 2}}, {'i', {'d', 2}},
{'i', {'m', 1}}, {'j', {'d', 2}}, {'j', {'e', 2}}, {'j', {'n', 1}}, {'k', {'e', 2}},
{'k', {'f', 2}}, {'k', {'o', 1}}, {'l', {'h', 1}}, {'m', {'i', 1}}, {'n', {'j', 1}},
{'o', {'k', 1}}};
std::multimap<Position, std::pair<Position, UInt>> valid_moves{
{0, {1, 1}}, {1, {0, 1}}, {1, {2, 2}}, {1, {7, 2}}, {2, {1, 2}}, {2, {3, 2}},
{2, {7, 2}}, {2, {8, 2}}, {3, {2, 2}}, {3, {4, 2}}, {3, {8, 2}}, {3, {9, 2}},
{4, {3, 2}}, {4, {5, 2}}, {4, {9, 2}}, {4, {10, 2}}, {5, {4, 2}}, {5, {6, 1}},
{5, {10, 2}}, {6, {5, 1}}, {7, {1, 2}}, {7, {2, 2}}, {7, {11, 1}}, {8, {2, 2}},
{8, {3, 2}}, {8, {12, 1}}, {9, {3, 2}}, {9, {4, 2}}, {9, {13, 1}}, {10, {4, 2}},
{10, {5, 2}}, {10, {14, 1}}, {11, {7, 1}}, {12, {8, 1}}, {13, {9, 1}}, {14, {10, 1}}};
std::map<Type, UInt> multipliers{{'A', 1}, {'B', 10}, {'C', 100}, {'D', 1000}};
@@ -47,6 +44,7 @@ struct State
auto size() const noexcept -> UInt { return 15; }
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)
{
@@ -75,42 +73,56 @@ struct State
abort();
}
bool move(unsigned from, unsigned to)
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;
}
constexpr bool operator<(State const& rhs) const noexcept { return nodes_ < rhs.nodes_; }
constexpr bool operator==(State const& rhs) const noexcept { return nodes_ < rhs.nodes_; }
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, 15> nodes_{'.'};
static std::array<Type, 15> finished_;
};
template<>
struct std::hash<State>
{
auto operator()(State const& key) const -> std::size_t
{
std::size_t result{0};
for (auto i{0}; i < 15; ++i) {
result <<= 3;
if (key.node(i) != '.') {
result |= key.node(i) - 'A' + 1;
}
}
return result;
}
UInt cost_{0};
};
std::array<Type, 15> State::finished_ = {'.', '.', '.', '.', '.', '.', '.', '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"(#(.)(.)\.(.)\.(.)\.(.)\.(.)(.)#)"};
@@ -124,7 +136,7 @@ auto main() -> int
std::cerr << "Incorrect first line.\n";
return 1;
}
State initial_state;
State* initial_state = new State;
std::getline(std::cin, line);
if (!std::regex_search(line, m, line2_re)) {
@@ -132,7 +144,7 @@ auto main() -> int
return 1;
}
for (unsigned i = 0; i < 7; ++i) {
initial_state.node(i) = m.str(i + 1)[0];
initial_state->node(i) = m.str(i + 1)[0];
}
std::getline(std::cin, line);
@@ -141,7 +153,7 @@ auto main() -> int
return 1;
}
for (unsigned i = 0; i < 4; ++i) {
initial_state.node(7 + i) = m.str(i + 1)[0];
initial_state->node(7 + i) = m.str(i + 1)[0];
}
std::getline(std::cin, line);
@@ -150,45 +162,63 @@ auto main() -> int
return 1;
}
for (unsigned i = 0; i < 4; ++i) {
initial_state.node(11 + i) = m.str(i + 1)[0];
initial_state->node(11 + i) = m.str(i + 1)[0];
}
std::map<State, UInt> states;
states.insert({initial_state, 0});
std::set<State> visited;
std::set<State*, StateCmp> states;
std::set<State*, CostStateCmp> costs;
std::set<State*, StateCmp> visited;
states.insert(initial_state);
costs.insert(initial_state);
while (!states.empty()) {
auto it{std::min_element(states.begin(), states.end(), [](auto const& lhs, auto const& rhs) {
return lhs.second < rhs.second;
})};
if (visited.size() % 10'000 == 0) {
std::cout << "Visited: " << visited.size() << " number of states: " << states.size()
<< " Min energy: " << it->second << '\n';
}
while (!costs.empty()) {
assert(costs.size() == states.size());
auto it{costs.begin()};
State state{it->first};
UInt cost{it->second};
State* state{*it};
visited.insert(state);
states.erase(state);
costs.erase(it);
if (state.finished()) {
std::cout << "Done with cost " << cost << '\n';
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) == '.') {
for (unsigned i = 0; i < state->size(); ++i) {
if (state->node(i) == '.') {
continue;
}
auto [it_begin, it_end] = costs.equal_range(i + 'a');
for (auto cost_it{it_begin}; cost_it != it_end; ++cost_it) {
State next_state{state};
if (next_state.move(i, cost_it->second.first - 'a') && !visited.contains(next_state)) {
UInt next_cost = cost + cost_it->second.second * multipliers[state.node(i)];
auto [insert_it, success] = states.insert({next_state, next_cost});
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) {
insert_it->second = std::min(insert_it->second, next_cost);
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;
}
}
}