《算法竞赛从入门到进阶》第四章 搜索技术 八数码问题和状态图搜索

八数码

#include<queue>
#include<stdio.h>
#include<iostream>
#include<string.h>
using namespace std;
const int LEN = 362880;
struct node
{
	int state[9];
	int dis;
};
int dir[4][2]={{-1,0},{0,-1},{1,0},{0,1}};
int visited[LEN]={0};
int start[9];
int goal[9];
long int factory[]={1,1,2,6,24,120,720,5040,40320,362880};
void swap(int a,int b)
{
  int c=0;
  c=a;
  a=b;
  b=c;	
} 
bool Cantor(int str[],int n)
{
	cout<<"hello"<<endl;
	long result = 0;
	for(int i=0;i<n;++i)
	{
		int counted=0;
		for(int j=i+1;j<n;j++)
		{
			if(str[i]>str[j])
			{
				++counted;
			}
		}
		result+=counted*factory[n-i-1];
	}
	if(!visited[result])
	{
		visited[result]=1;
		return 1;
	}
	else
	{
		return 0;
	}
	
}
int bfs()
{
	node head;
	memcpy(head.state,start,sizeof(head.state));
	head.dis=0;
	queue<node> q;
	Cantor(head.state,9);
	q.push(head);
	
	while(!q.empty())
	{
		head = q.front();
		q.pop();
		int z;
		for(z = 0;z<9;z++)
		{
			if(head.state[z]==0)
			{
				break;
			}
		}
		int x = z%3;
		int y = z/3;
		printf("head.state[%d]=%d",z,head.state[z]);
		for(int i=0;i<4;++i)
		{
			int newx = x + dir[i][0];
			int newy = y + dir[i][1];
			int nz = newx + 3*newy;
			if(newx>=0&&newx<3&&newy>=0&&newy<3)
			{
				node newnode;
				memcpy(&newnode,&head,sizeof(struct node));
				swap(newnode.state[z],newnode.state[nz]);
				newnode.dis++;
				
				if(memcmp(newnode.state,goal,sizeof(goal))==0)
				{
					return newnode.dis;
				}
				if(Cantor(newnode.state,9))
				{
					
					q.push(newnode);
				}
			}
		}
		
	}
	return -1;
}

int main()
{
	for(int i=0;i<9;++i) 
	{
		cin>>start[i];
//		cout<< start[i];
	}
	cout<<"输入的棋盘："<<endl;
	for(int i=1;i<=9;++i) 
	{
		cout<<start[i-1]<<" ";
		if(i%3==0)cout<<endl;
	}
	
	for(int i=0;i<9;++i) cin>>goal[i];
	cout<<"目标的棋盘："<<endl;
	for(int i=1;i<=9;++i) 
	{
		cout<<goal[i-1]<<" ";
		if(i%3==0)cout<<endl;
	}
	int num = bfs();
	if(num!=-1) 
	{
		cout<<num<<endl;
	}
	else
	{
		cout<<"Impossible"<<endl;
	}
	return 0;
 }