8 puzzle with A* algorithm

The main idea is from:

http://www.cs.princeton.edu/courses/archive/spr10/cos226/assignments/8puzzle.html

A* is used to find the best solution. The detail of A* could be found:

http://web.mit.edu/eranki/www/tutorials/search/

#include <iostream>#include <vector>#include <algorithm>#include <list>#include <queue>#include <unordered_map>#include <string>#include <sstream>#include <stdexcept>#include <memory>#include <Windows.h>using namespace std;class Board;class Solver;class Board{friend class Solver;friend class compare_node;public:typedef enum{TL_SPACE,TL_1,TL_2,TL_3,TL_4,TL_5,TL_6,TL_7,TL_8,}TILE;Board(){for (int i = 0; i != 8; tiles.push_back(TILE(++i)));tiles.push_back(TL_SPACE);}Board(int t[3][3]){for (int i = 0; i != 3; ++i)for (int j = 0; j != 3; ++j)tiles.push_back(TILE(t[i][j]));}int hamming(){int count = 0;for (int i = 0; i != tiles.size(); ++i)if (tiles[i] != TILE((i + 1)) && tiles[i] != TL_SPACE)++count;return count;}int manhattan(){int count = 0;int num;for (int i = 0; i != tiles.size(); ++i){if (tiles[i] == TL_SPACE)continue;num = (tiles[i] + 8) % 9;count = count + (abs(num / 3 - i / 3) + abs(num % 3 - i % 3));}return count;}bool equals(const Board &b) const{bool ret = true;for (int i = 0; i != b.tiles.size(); ++i){if (this->tiles[i] != b.tiles[i]){ret = false;break;}}return ret;}void neighbors(vector<Board> &nghbrs){nghbrs.clear();int pos = 0;for (; pos != tiles.size() && tiles[pos] != TL_SPACE; ++pos);int row = pos / 3;int col = pos % 3;if (row > 0){nghbrs.push_back(*this);nghbrs.back().swap(pos, (row - 1) * 3 + col);}if (row < 2){nghbrs.push_back(*this);nghbrs.back().swap(pos, (row + 1) * 3 + col);}if (col > 0){nghbrs.push_back(*this);nghbrs.back().swap(pos, row * 3 + col - 1);}if (col < 2){nghbrs.push_back(*this);nghbrs.back().swap(pos, row * 3 + col + 1);}}string toString(){string s;ostringstream convert;for (int i = 0; i != tiles.size(); ++i)convert << static_cast<int>(tiles[i]) << " ";s = convert.str();return s;}private:vector<TILE> tiles;Board *parent = nullptr;int f = 0;int g = 0;int h = 0;void swap(size_t pos1, size_t pos2){if (pos1 >= tiles.size() || pos2 >= tiles.size())throw runtime_error("position not match");std::swap(tiles[pos1], tiles[pos2]);}};// function used to compared board in heapclass compare_node{public:bool operator()(Board *&l, Board *&r){return l->f > r->f;}};// vector for board pointersclass bvector : public vector<Board*>{public:bvector(){make_heap(this->begin(), this->end(), compare_node());}void push_node(Board *b){this->push_back(b);push_heap(this->begin(), this->end(), compare_node());}void pop_node(){pop_heap(this->begin(), this->end(), compare_node());this->pop_back();}};class Solver{friend class Board;public:Solver() = default;Solver(Board *p) : initial(p) {}void init(){if (initial == nullptr){cerr << "Solver not initialized" << endl;return;}if (!isSolvable()){cerr << "No solution existed" << endl;return;}initial->g = 0;initial->h = initial->manhattan() + initial->hamming();initial->f = initial->g + initial->h;open_ref[initial->toString()] = initial;open_set.push_node(initial);while (!open_set.empty()){Board *closed_node = open_set.front();open_ref.erase(closed_node->toString());closed_ref[closed_node->toString()] = closed_node;open_set.pop_node();if (closed_node->equals(*end)){Board *p = closed_node;while (p->parent != nullptr){solution.push_back(p->toString());p = p->parent;}solution.push_back(initial->toString());reverse(solution.begin(), solution.end());return;}vector<Board> neighbors;closed_node->neighbors(neighbors);for (auto iter = neighbors.begin(); iter != neighbors.end(); ++iter){Board *new_node = new Board(*iter);new_node->g = 0;new_node->h = new_node->manhattan() + new_node->hamming();new_node->f = new_node->f + new_node->h;// ignore the neighbor which is already evaluated.if (closed_ref.find(new_node->toString()) != closed_ref.end()){delete new_node;continue;}if (open_ref.find(new_node->toString()) != open_ref.end()){delete new_node;continue;}new_node->parent = closed_node;open_set.push_node(new_node);open_ref[new_node->toString()] = new_node;}}return;}vector<string> getSolution(){return solution;}// http://www.geeksforgeeks.org/check-instance-8-puzzle-solvable/// It is not possible to solve an instance of 8 puzzle if the number of inversions is odd// in the initial statebool isSolvable(){int count = 0;for (int i = 0; i != initial->tiles.size(); ++i)for (int j = i + 1; j != initial->tiles.size(); ++j)if (initial->tiles[i] != Board::TILE::TL_SPACE &&initial->tiles[j] != Board::TILE::TL_SPACE &&static_cast<int>(initial->tiles[i]) > static_cast<int>(initial->tiles[j]))++count;return (count % 2 == 0);}~Solver(){delete initial;delete end;for (auto iter = open_ref.begin(); iter != open_ref.end(); ++iter)delete iter->second;for (auto iter = closed_ref.begin(); iter != closed_ref.end(); ++iter)delete iter->second;}private:Board *initial = nullptr;Board *end = new Board();bvector open_set;unordered_map<string, Board*> open_ref;unordered_map<string, Board*> closed_ref;vector<string> solution;};int main(){int t1[3][3] = { { 1, 2, 3 },{ 4, 5, 6 },{ 8, 7, 0 } };int t2[3][3] = { { 8, 1, 3 },{ 4, 0, 2 },{ 7, 6, 5 } };Board *b1 = new Board(t1);Board *b2 = new Board(t2);Solver s1(b1);Solver s2(b2);s1.init(); s2.init();auto ret2 = s2.getSolution();cout << "The solution to " << b1->toString() << endl;for (auto str : ret2)cout << str << endl;system("PAUSE");return 0;}