问题描述:
将8-魔方的起始状态在有限移动步骤内,转换为目标状态,如下图所示。
算法思路:
通过优先队列实现相似度比对,当相似度为9,即当前状态与目标状态一致时,返回当前路径。
源码:
/*
8-cube problem-Best-First algorithm
15S103182
Ethan
2015.12.21
*/
#include <iostream>
#include <vector>
#include <queue>
#include <fstream>
#include <sstream>
using namespace std ;
class cube{
public:
vector<vector<int> > m;
int similarity;
int x;// 0::i
int y;// 0::j
vector<string> path;//up down left right
cube(vector<vector<int> > a,int b):m(a),similarity(b){}
void pos(){//0-position
for(int i=0;i<m.size();i++){
for(int j=0;j<m[i].size();j++){
if(m[i][j]==0){
x = i;
y = j;
return ;
}
}
}
}
};
bool operator < (const cube& a,const cube& b){
return a.similarity<=b.similarity;
}
int stringToInt(string i){
stringstream sf;
int score=0;
sf<<i;
sf>>score;
return score;
}
cube openFile(const char* dataset){
fstream file;
file.open(dataset,ios::in);
vector<vector<int> > data;
while(!file.eof()){
vector<int> tv;
char temp[8];
file.getline(temp,6);
tv.push_back(temp[0]-48);
tv.push_back(temp[2]-48);
tv.push_back(temp[4]-48);
data.push_back(tv) ;
}
file.close();
cube res(data,0);
return res;
}
void output(vector<vector<int> > m){
for(int i=0;i<m.size();i++){
for(int j=0;j<m[i].size();j++){
cout<<m[i][j]<<" ";
}
cout<<endl;
}
}
int calSimilarity(cube a,cube t){
int s = 0;
for(int i=0;i<3;i++){
for(int j=0;j<3;j++){
if(a.m[i][j]==t.m[i][j])
s++;
}
}
return s;
}
vector<cube> move(const cube& v){
vector<cube> res;
if(v.x>0){
cube a(v);
a.m[a.x][a.y] = a.m[a.x-1][a.y];
a.m[a.x-1][a.y] = 0;
a.x--;
a.path.push_back("down");
res.push_back(a);
}
if(v.x<2){
cube a(v);
a.m[a.x][a.y] = a.m[a.x+1][a.y];
a.m[a.x+1][a.y] = 0;
a.x++;
a.path.push_back("up");
res.push_back(a);
}
if(v.y>0){
cube a(v);
a.m[a.x][a.y] = a.m[a.x][a.y-1];
a.m[a.x][a.y-1] = 0;
a.y--;
a.path.push_back("right");
res.push_back(a);
}
if(v.y<2){
cube a(v);
a.m[a.x][a.y] = a.m[a.x][a.y+1];
a.m[a.x][a.y+1] = 0;
a.y++;
a.path.push_back("left");
res.push_back(a);
}
return res;
}
void eightCube(cube orginal,cube target){
priority_queue<cube,vector<cube>,less<cube> > pq;
vector<cube> copy;
orginal.similarity = calSimilarity(orginal,target);
orginal.pos();
pq.push(orginal);
copy.push_back(orginal);
while(!pq.empty()){//best-first
cube v = pq.top();
pq.pop();
vector<cube> ms = move(v);
for(int i=0;i<ms.size();i++){
ms[i].similarity = calSimilarity(ms[i],target);
ms[i].pos();
int flag = 1;
for(int j=copy.size()-1;j>=0;j--){
if(calSimilarity(ms[i],copy[j])==9){
flag = 0;
break;
}
}
if(flag){
if(ms[i].similarity==9){
cout<<"Path:"<<endl;
cout<<"orginal --> ";
for(int k=0;k<ms[i].path.size();k++){
cout<<ms[i].path[k]<<" --> ";
}
cout<<"target"<<endl;
return ;
}
pq.push(ms[i]);
copy.push_back(ms[i]);
}
}
}
}
int main()
{
eightCube(openFile("original.txt"),openFile("target.txt"));
}
测试:
起始状态:
5 6 7
2 0 3
1 4 8
目标状态:
1 2 3
4 5 6
7 8 0
移动路径: