487 lines
11 KiB
C++
487 lines
11 KiB
C++
#include <cstdint>
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#include <iostream>
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#include <map>
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#include <numeric>
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#include <optional>
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#include <set>
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#include <sstream>
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#include <string>
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#include <tuple>
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#include <queue>
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#include <doctest.h>
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#include <aocpp/Startup.hpp>
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#include <aocpp/Grid.hpp>
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using namespace aocpp;
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namespace {
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auto IsUnit(char c) -> bool {
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return c == 'G' || c == 'E';
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}
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auto IsOpposed(char x, char y) -> bool {
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return x == 'G' && y == 'E' || x == 'E' && y == 'G';
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}
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struct IsBefore {
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auto operator()(Coord const& a, Coord const& b) const -> bool {
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return a.y < b.y || a.y == b.y && a.x < b.x;
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}
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};
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int const initial_hp = 200;
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Coord const reading_order[] {{0,-1}, {-1,0}, {1,0}, {0,1}};
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struct Game {
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Grid grid_;
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std::map<Coord, int> units_;
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int e_damage_;
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int g_damage_;
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bool no_elves_can_die;
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std::ostream * debug_out_;
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Game(Grid grid);
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auto Simulate() -> std::optional<int>;
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auto PickTarget(Coord my_coord, char my_team)
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-> std::map<Coord, int>::iterator;
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auto Move(Coord my_coord, char my_team) -> std::optional<Coord>;
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};
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Game::Game(Grid grid)
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: grid_(std::move(grid))
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, units_{}
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, e_damage_(3)
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, g_damage_(3)
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, no_elves_can_die{false}
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, debug_out_{}
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{
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// set each unit to its initial hit points
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for (auto [k, v] : grid_) {
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if (IsUnit(v)) {
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units_[k] = initial_hp;
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}
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}
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}
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// Render the game as seen in the examples
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auto operator<<(std::ostream & out, Game const& game) -> std::ostream & {
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for (std::size_t y = 0; y < game.grid_.rows.size(); ++y) {
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out << game.grid_.rows[y];
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bool first = true;
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for (std::size_t x = 0; x < game.grid_.rows[y].size(); ++x) {
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auto c = game.grid_.rows[y][x];
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if (IsUnit(c)) {
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if (first) {
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first = false;
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out << " ";
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} else {
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out << ", ";
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}
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Coord const coord {std::int64_t(x),std::int64_t(y)};
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out << c << "(" << game.units_.at(coord) << ")";
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}
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}
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out << std::endl;
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}
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return out;
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}
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// Determine the best target to attack from the current position, if there is one.
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auto Game::PickTarget(Coord my_coord, char my_team) -> std::map<Coord, int>::iterator
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{
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std::map<Coord, int>::iterator best = units_.end();
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for (auto const dir : reading_order) {
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auto const here = dir + my_coord;
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if (IsOpposed(my_team, grid_[here])) {
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auto it = units_.find(here);
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if (best == units_.end() || best->second > it->second) {
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best = it;
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}
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}
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}
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return best;
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}
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// Determine the best location to move to, if there is one.
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auto Game::Move(Coord my_coord, char my_team) -> std::optional<Coord>
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{
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std::optional<Coord> best_start;
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Coord best_end; // initialized when best_start is non-empty
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int best_distance; // initialized when best_start is non-empty
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std::queue<std::tuple<Coord, Coord, int>> todo;
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for (auto const dir : reading_order) {
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auto const start = my_coord + dir;
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if (grid_[start] == '.') {
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todo.push({start, start, 1});
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}
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}
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std::set<Coord> seen;
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while (!todo.empty()) {
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auto const [start, cursor, steps] = todo.front();
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todo.pop();
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if (best_start) {
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if (best_distance < steps) break;
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if (best_start && !IsBefore()(cursor, best_end)) continue;
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} else {
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if (!seen.insert(cursor).second) { continue; }
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for (auto const dir : reading_order) {
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auto const next = cursor + dir;
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if (grid_[next] == '.') {
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todo.push({start, cursor + dir, steps+1});
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}
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}
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}
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if (PickTarget(cursor, my_team) != units_.end()) {
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best_start = start;
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best_end = cursor;
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best_distance = steps;
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}
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}
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return best_start;
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}
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auto Game::Simulate() -> std::optional<int> {
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for (int rounds = 0;; rounds++) {
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if (debug_out_) {
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*debug_out_ << "After " << rounds << " rounds:" << std::endl
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<< *this << std::endl;
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}
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// determine order of unit updates
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std::set<Coord, IsBefore> turn_order;
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for (auto const& [k,_] : units_) {
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turn_order.insert(k);
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}
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for (auto active_coord : turn_order) {
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auto const active_team = grid_[active_coord];
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// Detect when no targets remain for this unit and end the game
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auto game_over = true;
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for (auto [k, v] : grid_) {
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if (IsOpposed(active_team, v)) game_over = false;
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}
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if (game_over) {
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int total_hp = 0;
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for (auto const& [_,v] : units_) { total_hp += v; }
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return {rounds * total_hp};
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}
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// Try to pick a target without moving
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auto target = PickTarget(active_coord, active_team);
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// only move when necessary
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if (target == units_.end()) {
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// move if we can
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if (auto const destination = Move(active_coord, active_team)) {
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std::swap(grid_[*destination], grid_[active_coord]);
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auto const it = units_.find(active_coord);
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units_[*destination] = it->second;
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units_.erase(it);
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active_coord = *destination;
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}
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target = PickTarget(active_coord, active_team);
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}
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// target in range, do the attack
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if (target != units_.end()) {
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auto & [target_coord, target_hp] = *target;
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auto damage = active_team == 'G' ? g_damage_ : e_damage_;
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// lethal
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if (target_hp <= damage) {
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if (no_elves_can_die && grid_[target_coord] == 'E') return {};
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grid_[target_coord] = '.';
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turn_order.erase(target_coord);
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units_.erase(target); // invalidates target, target_coord, target_hp
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} else {
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target_hp -= damage;
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}
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}
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}
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}
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}
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auto Part2(Game game) {
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game.no_elves_can_die = true;
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int best;
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auto const attempt = [&](int const power) {
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auto g = game;
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g.e_damage_ = power;
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return g.Simulate();
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};
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int too_low = 3;
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int high = 4;
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for(;;) {
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if (auto outcome = attempt(high)) {
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best = *outcome; break;
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}
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too_low = high;
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high *= 2;
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}
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while (too_low+1 < high) {
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auto x = std::midpoint(too_low, high);
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if (auto outcome = attempt(x)) {
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best = *outcome; high = x;
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} else {
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too_low = x;
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}
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}
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return std::make_pair(best, high);
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}
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} // namespace
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TEST_SUITE("2018-15 examples") {
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auto case1(int expect, std::string start, std::string end) -> void {
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std::istringstream in { std::move(start) };
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std::ostringstream out;
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Game game {Grid::Parse(in)};
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auto outcome = game.Simulate();
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out << game;
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CHECK(out.str() == end);
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CHECK(outcome == std::optional<int>{expect});
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}
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TEST_CASE("example 1") {
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case1(27730,
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"#######\n"
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"#.G...#\n"
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"#...EG#\n"
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"#.#.#G#\n"
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"#..G#E#\n"
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"#.....#\n"
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"#######\n",
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"#######\n"
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"#G....# G(200)\n"
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"#.G...# G(131)\n"
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"#.#.#G# G(59)\n"
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"#...#.#\n"
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"#....G# G(200)\n"
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"#######\n");
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}
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TEST_CASE("example 2") {
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case1(36334,
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"#######\n"
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"#G..#E#\n"
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"#E#E.E#\n"
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"#G.##.#\n"
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"#...#E#\n"
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"#...E.#\n"
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"#######\n",
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"#######\n"
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"#...#E# E(200)\n"
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"#E#...# E(197)\n"
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"#.E##.# E(185)\n"
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"#E..#E# E(200), E(200)\n"
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"#.....#\n"
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"#######\n");
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}
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TEST_CASE("example 3") {
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case1(39514,
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"#######\n"
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"#E..EG#\n"
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"#.#G.E#\n"
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"#E.##E#\n"
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"#G..#.#\n"
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"#..E#.#\n"
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"#######\n",
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"#######\n"
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"#.E.E.# E(164), E(197)\n"
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"#.#E..# E(200)\n"
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"#E.##.# E(98)\n"
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"#.E.#.# E(200)\n"
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"#...#.#\n"
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"#######\n");
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}
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TEST_CASE("example 4") {
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case1(27755,
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"#######\n"
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"#E.G#.#\n"
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"#.#G..#\n"
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"#G.#.G#\n"
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"#G..#.#\n"
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"#...E.#\n"
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"#######\n",
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"#######\n"
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"#G.G#.# G(200), G(98)\n"
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"#.#G..# G(200)\n"
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"#..#..#\n"
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"#...#G# G(95)\n"
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"#...G.# G(200)\n"
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"#######\n");
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}
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TEST_CASE("example 5") {
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case1(28944,
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"#######\n"
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"#.E...#\n"
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"#.#..G#\n"
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"#.###.#\n"
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"#E#G#G#\n"
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"#...#G#\n"
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"#######\n",
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"#######\n"
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"#.....#\n"
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"#.#G..# G(200)\n"
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"#.###.#\n"
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"#.#.#.#\n"
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"#G.G#G# G(98), G(38), G(200)\n"
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"#######\n");
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}
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TEST_CASE("example 6") {
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case1(18740,
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"#########\n"
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"#G......#\n"
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"#.E.#...#\n"
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"#..##..G#\n"
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"#...##..#\n"
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"#...#...#\n"
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"#.G...G.#\n"
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"#.....G.#\n"
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"#########\n",
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"#########\n"
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"#.G.....# G(137)\n"
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"#G.G#...# G(200), G(200)\n"
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"#.G##...# G(200)\n"
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"#...##..#\n"
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"#.G.#...# G(200)\n"
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"#.......#\n"
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"#.......#\n"
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"#########\n"
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);
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}
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auto case2(int expect, std::string start, std::string end) -> void {
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std::istringstream in { std::move(start) };
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std::ostringstream out;
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Game game {Grid::Parse(in)};
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auto [outcome, e_damage] = Part2(game);
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game.e_damage_ = e_damage;
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game.Simulate();
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out << game;
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CHECK(out.str() == end);
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CHECK(outcome == expect);
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}
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TEST_CASE("example 7") {
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case2(4988,
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"#######\n"
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"#.G...#\n"
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"#...EG#\n"
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"#.#.#G#\n"
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"#..G#E#\n"
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"#.....#\n"
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"#######\n",
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"#######\n"
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"#..E..# E(158)\n"
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"#...E.# E(14)\n"
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"#.#.#.#\n"
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"#...#.#\n"
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"#.....#\n"
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"#######\n"
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);
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}
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TEST_CASE("example 8") {
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case2(31284,
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"#######\n"
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"#E..EG#\n"
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"#.#G.E#\n"
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"#E.##E#\n"
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"#G..#.#\n"
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"#..E#.#\n"
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"#######\n",
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"#######\n"
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"#.E.E.# E(200), E(23)\n"
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"#.#E..# E(200)\n"
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"#E.##E# E(125), E(200)\n"
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"#.E.#.# E(200)\n"
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"#...#.#\n"
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"#######\n");
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}
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TEST_CASE("example 9") {
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case2(3478,
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"#######\n"
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"#E.G#.#\n"
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"#.#G..#\n"
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"#G.#.G#\n"
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"#G..#.#\n"
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"#...E.#\n"
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"#######\n",
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"#######\n"
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"#.E.#.# E(8)\n"
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"#.#E..# E(86)\n"
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"#..#..#\n"
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"#...#.#\n"
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"#.....#\n"
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"#######\n");
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}
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TEST_CASE("example 10") {
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case2(6474,
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"#######\n"
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"#.E...#\n"
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"#.#..G#\n"
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"#.###.#\n"
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"#E#G#G#\n"
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"#...#G#\n"
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"#######\n",
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"#######\n"
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"#...E.# E(14)\n"
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"#.#..E# E(152)\n"
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"#.###.#\n"
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"#.#.#.#\n"
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"#...#.#\n"
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"#######\n");
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}
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TEST_CASE("example 11") {
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case2(1140,
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"#########\n"
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"#G......#\n"
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"#.E.#...#\n"
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"#..##..G#\n"
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"#...##..#\n"
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"#...#...#\n"
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"#.G...G.#\n"
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"#.....G.#\n"
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"#########\n",
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"#########\n"
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"#.......#\n"
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"#.E.#...# E(38)\n"
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"#..##...#\n"
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"#...##..#\n"
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"#...#...#\n"
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"#.......#\n"
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"#.......#\n"
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"#########\n");
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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 const grid {Grid::Parse(in)};
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Game game {std::move(grid)};
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//game.debug_out_ = &out;
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out << "Part 1: " << *Game{game}.Simulate() << std::endl;
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out << "Part 2: " << Part2(std::move(game)).first << std::endl;
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}
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