POJ 1753/BFS:翻转棋

黑白棋翻转

4X4的棋盘有2^16种状态，如果状态值为0或65535则算法结束

第一层：初始状态

第二层：初始状态翻0、初始状态翻1、初始状态翻……初始状态翻15

第三层:  ………………………….

如果该状态值未访问过，则入队列

#include <iostream>

#define MAX_STATE 65535

#define ALL_BLACK 65535

#define ALL_WHITE 0

#define WIDTH 4

#define HEIGTH 4

#define SIZE_OF_BOARD WIDTH*HEIGTH

#include <queue>



using namespace std;



int flip(int current,int pos){

	current ^=1<<pos;

	if(pos>=WIDTH)current ^=1<<(pos-WIDTH);

	if(pos+WIDTH<SIZE_OF_BOARD)current ^=1<<(pos+WIDTH);

	if(pos%WIDTH!=0)current ^=1<<(pos-1);

	if(pos%WIDTH!=WIDTH-1)current ^=1<<(pos+1);

	return current;

}

int main(int argc, char* argv[])

{

	

	

	int step[MAX_STATE];

	int current_state = 0,next_state;

//	for(int i=0;i<HEIGTH;i++)

//	{

//		for(int j=0;j<WIDTH;j++)

//			current_state += (getchar()=='b')<<(i*WIDTH+j);

//		getchar();	

//		

//	}

	//debug("%d",8^2);

	char c;

	for(int i=0;i<SIZE_OF_BOARD;i++)

	{

		cin>>c;

		current_state += (c=='b')<<(i);

		//debug("%d",c);

	}

	if(current_state==ALL_WHITE||ALL_BLACK==current_state){

		printf("0\n");

		return 0;

	}

	memset(step,-1,MAX_STATE);

	queue<int> q;

	q.push(current_state);

	step[current_state]=0;

	//debug("%d",current_state);

	while(!q.empty()){

		current_state = q.front();

		q.pop();

		//debug("%d",current_state);

		for(int i=0;i<SIZE_OF_BOARD;i++)

		{

			next_state = flip(current_state,i);

			

			if(next_state==ALL_WHITE||next_state==ALL_BLACK){

				printf("%d\n",step[current_state]+1);

				return 0;

			}

			if(-1==step[next_state]){

				step[next_state] = step[current_state]+1;

				q.push(next_state);

			}

		}

		

	}

	printf("Impossible\n");

	//debug("%d",current_state);

	

	

	return 0;

}