POJ 1077 Eight bfs

        这题一开始做，什么优化都没做， 直接MLM+TLM, 后来用了康托展开+双向bfs过了，注意这题答案不唯一，开始与sample给的例子不同，以为自己错了，后来发现两个都对，果断交上去，结果AC掉了~

#include <iostream>
#include <string>
#include <queue>
#include <memory.h>
using namespace std;

struct status
{
	int x_x, x_y;
	int a;
	string path;
};
int fact[] = {1, 1, 2, 6, 24, 120, 720, 5040, 40320, 362880};
int isvisit[362880];
string path[362880];
char oper_name[] = {'u','d','l','r'};
char opposite_oper[] = {'d', 'u', 'r', 'l'};

bool do_operate(int, const status&, status&);
void bfs();
bool is_goal(const status&);
int encode(int);

int start;
int goal = 123456789;
int x_x, x_y;

int main()
{
	char c;
	
	int tmp[9];
	memset(isvisit, false, sizeof(isvisit));  

	while (cin >> c)
	{

		for (int i = 0; i < 3; i++)
			for (int j = 0; j < 3; j++)
			{		
				if (c == 'x')
				{
					tmp[3*i+j] = 9;
					x_x = i;
					x_y = j;
				}
				else
					tmp[3*i+j] = c - '0';
				if (!(i == 2 && j == 2))
					cin >> c;
			}
		start = tmp[0]*1e8 + tmp[1]*1e7 + tmp[2]*1e6 + tmp[3]*1e5 + tmp[4]*1e4 + tmp[5]*1e3 + tmp[6]*1e2 + tmp[7]*10 + tmp[8];
		bfs();
		memset(isvisit, false, sizeof(isvisit));  
	}
	return 0;
}

void bfs()
{
	queue<status> Q1, Q2;
	bool flag;
	status p, next;
	p.a = start;
	p.path = "";
	p.x_x = x_x;
	p.x_y = x_y;
	int code;
	isvisit[encode(p.a)] = 1;
	Q1.push(p);

	p.a = goal;
	p.x_x = 2;
	p.x_y = 2;
	isvisit[encode(p.a)] = 2;
	Q2.push(p);
	while (!Q1.empty())
	{
		p = Q1.front();
		Q1.pop();

		if (p.a == goal)
		{
			cout << p.path << endl;
			return ;
		}

		for (int i = 0; i < 4; i++)
		{
			flag = do_operate(i, p, next);
			next.path = p.path + oper_name[i];
			code = encode(next.a);
			if (flag )
			{
				if (isvisit[code] == 0)
				{
			    	isvisit[code] = 1;
					path[code] = next.path;
				    Q1.push(next);
				}
				else if (isvisit[code] == 2)
				{
					cout << next.path << path[code] << endl;
					return;
				}
			}
		}

		p = Q2.front();
		Q2.pop();

		for (int i = 0; i < 4; i++)
		{
			flag = do_operate(i, p, next);
			next.path = opposite_oper[i]+p.path;
			code = encode(next.a);
			if (flag)
			{
				if (isvisit[code] == 0)
				{
					isvisit[code] = 2;
					path[code] = next.path;
					Q2.push(next);
				}
				else if (isvisit[code] == 1)
				{
					cout <<  path[code]  << next.path << endl;
					return;
				}
			}
		}

	}

	cout << "unsolvable" << endl;

}

bool do_operate(int mode, const status& p, status & s)
{
	s = p;
	int num = p.a;
	int tmp[9];

	for (int i = 8; i >= 0; i--)
	{
		tmp[i] = num%10;
		num /= 10;
	}

	switch (mode)
	{
	case 0:
		if (p.x_x > 0)
		{
			swap(tmp[3*s.x_x + s.x_y],tmp[3*(s.x_x-1) + s.x_y]);
			s.x_x = s.x_x-1;
			s.x_y = s.x_y;
			s.a = tmp[0]*1e8 + tmp[1]*1e7 + tmp[2]*1e6 + tmp[3]*1e5 + tmp[4]*1e4 + tmp[5]*1e3 + tmp[6]*1e2 + tmp[7]*10 + tmp[8];
		}
		else
			return false;
		break;
	case 1:
		if (p.x_x < 2)
		{
			swap(tmp[3*s.x_x + s.x_y],tmp[3*(s.x_x+1) + s.x_y]);
		    s.x_x = p.x_x+1;
			s.x_y = p.x_y;
			s.a = tmp[0]*1e8 + tmp[1]*1e7 + tmp[2]*1e6 + tmp[3]*1e5 + tmp[4]*1e4 + tmp[5]*1e3 + tmp[6]*1e2 + tmp[7]*10 + tmp[8];
		}
		else
			return false;
		break;
	case 2:
		if (p.x_y > 0)
		{
			swap(tmp[3*s.x_x + s.x_y],tmp[3*(s.x_x) + s.x_y-1]);
			s.x_x = p.x_x;
			s.x_y = p.x_y-1;
			s.a = tmp[0]*1e8 + tmp[1]*1e7 + tmp[2]*1e6 + tmp[3]*1e5 + tmp[4]*1e4 + tmp[5]*1e3 + tmp[6]*1e2 + tmp[7]*10 + tmp[8];
		}
		else
			return false;
		break;
	case 3:
		if (p.x_y < 2)
		{
			swap(tmp[3*s.x_x + s.x_y],tmp[3*(s.x_x) + s.x_y+1]);
			s.x_x = p.x_x;
			s.x_y = p.x_y+1;
			s.a = tmp[0]*1e8 + tmp[1]*1e7 + tmp[2]*1e6 + tmp[3]*1e5 + tmp[4]*1e4 + tmp[5]*1e3 + tmp[6]*1e2 + tmp[7]*10 + tmp[8];
		}
		else
			return false;
		break;
	}

	return true;
}


int encode(int num)
{
	int tmp[9];
	int cnt;

	for (int i = 8; i >= 0; i--)
	{
		tmp[i] = num%10;
		num /= 10;
	}

	for (int i = 0; i < 9; i++)
	{
		cnt = 0;
		for (int j = i+1; j < 9; j++)
			if (tmp[i] > tmp[j]) cnt++;

		num += cnt*fact[8-i];
	}

	return num;
}