hdu 149 勝利大逃亡(續)

http://acm.hdu.edu.cn/showproblem.php?pid=1429

第一次接觸位運算，被坑了好久，一直不知道怎麼標記，代碼有點亂

#include<stdio.h>
#include<queue>
#include<string.h>
using namespace std;
int n,m,t;
char map[20][20];
int mov[4][2] = {1,0,0,1,-1,0,0,-1};
struct node
{
	int x,y,step;
	int letter;
};
bool book[20][20][1026];
int bfs(int sx,int sy)
{
	memset(book,0,sizeof(book));
	queue<node>q;
	node p1,p2;
	p1.x = sx;
	p1.y = sy;
	p1.step = 0;
	p1.letter = 0;
	q.push(p1);
	while(!q.empty())
	{
		p1 = q.front();
		q.pop();
		int next_x,next_y;
		for(int i = 0;i<4;i++)
		{
			p2 = p1;
			next_x = p1.x+mov[i][0];
			next_y = p1.y+mov[i][1];
			if(p1.step+1>=t)break;
			if(next_x<0 || next_y<0 || next_x>n-1 || next_y>m-1)
				continue;
			if(map[next_x][next_y]=='^')return p1.step+1;
			if(map[next_x][next_y]<='z' && map[next_x][next_y]>='a')
			{
				if(book[next_x][next_y][p1.letter | 1<<(map[next_x][next_y]-'a')] == true)continue;
				p2.letter = (p1.letter | 1<<(map[next_x][next_y]-'a'));
			}
			if(map[next_x][next_y]<='Z' && map[next_x][next_y]>='A')
			{
				if((p1.letter & 1<<(map[next_x][next_y]-'A'))==0)
					continue;
			}
			if(book[next_x][next_y][p1.letter] == false && map[next_x][next_y]!='*')
			{
				p2.step = p1.step+1;
				p2.x = next_x;
				p2.y = next_y;
				book[next_x][next_y][p1.letter] = true;
				q.push(p2);
			}
		}
	}
	return -1;
}
int main()
{
	int sx,sy;
	while(scanf("%d%d%d",&n,&m,&t)!=EOF)
	{
		getchar();
		for(int i = 0;i<n;i++)
		{
			for(int j = 0;j<m;j++)
			{
				scanf("%c",&map[i][j]);
				if(map[i][j]=='@')
					sx = i,sy = j;
			}
			getchar();
		}
		printf("%d\n",bfs(sx,sy));
	}
	return 0;
}