#include <iostream>#include <list>#include <string>#include <tuple>#include <algorithm>#include <boost/foreach.hpp>using namespace std;typedef pair<int, int> Position;inline Position operator+(const Position& p1, const Position& p2){return Position(p1.first + p2.first, p1.second + p2.second);}inline unsigned int myabs(int i){return static_cast<unsigned int>(i < 0 ? -i : i);}Position offset[] = {Position(0, -1),Position(0, 1),Position(-1, 0),Position(1, 0),};struct puz_game{Position m_size;string m_start, m_goal;Position m_space;puz_game(int r, int c, const string& start, const string& goal);int rows() const {return m_size.first;}int cols() const {return m_size.second;}};puz_game::puz_game(int r, int c, const string& start, const string& goal): m_size(r, c), m_start(start), m_goal(goal){int n = m_start.find(' ');m_space = Position(n / cols(), n % cols());}struct puz_state : string{puz_state() {}puz_state(const puz_game& g): string(g.m_start), m_game(&g), m_space(g.m_space), m_move(0) {}int rows() const {return m_game->rows();}int cols() const {return m_game->cols();}char cell(int r, int c) const {return at(r * cols() + c);}char& cell(const Position& p) {return (*this)[p.first * cols() + p.second];}bool is_valid(const Position& p) const {return p.first >= 0 && p.first < rows() && p.second >= 0 && p.second < cols();}void make_move(const Position& p, char move){cell(m_space) = cell(p);cell(m_space = p) = ' ';m_move = move;}//puz_solver_idastar interfacebool is_goal_state() const {return *this == m_game->m_goal;}void gen_children(list<puz_state>& children) const;unsigned int get_heuristic() const;unsigned int get_distance(const puz_state& child) const {return 1;}const puz_game* m_game;Position m_space;char m_move;};void puz_state::gen_children(list<puz_state> &children) const{char* moves = "wens";for(int i = 0; i < 4; ++i){Position p = m_space + offset[i];if(is_valid(p)){children.push_back(*this);children.back().make_move(p, moves[i]);}}}unsigned int puz_state::get_heuristic() const{unsigned int md = 0;for(size_t i = 0; i < size(); ++i) {size_t j = m_game->m_goal.find(at(i));md += myabs(j / cols() - i / cols()) + myabs(j % cols() - i % cols());}return md;}ostream& operator<<(ostream& out, const puz_state& s){if(s.m_move)out << "move: " << s.m_move << endl;for(int r = 0; r < s.rows(); ++r) {for(int c = 0; c < s.cols(); ++c)out << s.cell(r, c) << ' ';out << endl;}return out;}template<class puz_state>class puz_solver_idastar{static bool dfs(unsigned int start_cost, const puz_state& cur,unsigned int cost_limit, unsigned int& next_cost_limit,list<puz_state>& spath, size_t& examined){++examined;unsigned int minimum_cost = start_cost + cur.get_heuristic();if(minimum_cost > cost_limit)return next_cost_limit = min(next_cost_limit, minimum_cost), false;if(cur.is_goal_state())return next_cost_limit = cost_limit, true;list<puz_state> children;cur.gen_children(children);BOOST_FOREACH(const puz_state& child, children){// full cycle checkingif(find(spath.begin(), spath.end(), child) != spath.end())continue;unsigned int new_start_cost = start_cost + cur.get_distance(child);spath.push_back(child);bool found = dfs(new_start_cost, child, cost_limit, next_cost_limit, spath, examined);if(found)return true;spath.pop_back();}return false;}public:static pair<bool, size_t> find_solution(const puz_state& sstart, list<puz_state>& spath){unsigned int inf = numeric_limits<unsigned int>::max();unsigned int cost_limit = sstart.get_heuristic(), next_cost_limit = inf;size_t examined = 0;spath.assign(1, sstart);for(;;){bool found = dfs(0, sstart, cost_limit, next_cost_limit, spath, examined);if(found)return make_pair(true, examined);if(next_cost_limit == inf)return make_pair(false, examined);cost_limit = next_cost_limit, next_cost_limit = inf;}}};int main(){// start state// 2 8 3// 1 6 4// 7 5// goal state// 1 2 3// 8 4// 7 6 5puz_game g(3, 3, "2831647 5", "1238 4765");list<puz_state> spath;bool found;size_t examined;tie(found, examined) = puz_solver_idastar<puz_state>::find_solution(g, spath);if(found){cout << "Sequence of moves: " << endl;BOOST_FOREACH(const puz_state& s, spath)cout << s;cout << "Number of moves: " << spath.size() - 1 << endl;}cout << "Number of states examined: " << examined << endl;}/*Sequence of moves:2 8 31 6 47 5move: n2 8 31 47 6 5move: n2 31 8 47 6 5move: w 2 31 8 47 6 5move: s1 2 3 8 47 6 5move: e1 2 38 47 6 5Number of moves: 5Number of states examined: 19*/
