双端队列广搜WA on #8

#include<bits/stdc++.h>
using namespace std;
int n,sx,sy,ex,ey,x,y,z,b[105][105][4],xx,yy,zz,dx[4]={-1,0,1,0},dy[4]={0,1,0,-1};
char a[105][105];
struct node
{
	int x,y,f;
};
deque<node> d;
int main()
{
	memset(b,-1,sizeof(b));
	cin>>n;
	for (int i=1;i<=n;++i)
	for (int j=1;j<=n;++j)
	{
		cin>>a[i][j];
		if (a[i][j]=='A')
		{
			sx=i;
			sy=j;
		}
		else if (a[i][j]=='B')
		{
			ex=i;
			ey=j;
		}
	}
	for (int i=0;i<4;++i)
	{
		b[sx][sy][i]=0;
		d.push_back((node){sx,sy,i});
	}
	while (!d.empty())
	{
		x=d.front().x;
		y=d.front().y;
		z=d.front().f;
		d.pop_front();
		xx=x+dx[z];
		yy=y+dy[z];
		if (0<xx && xx<=n && 0<yy && yy<=n && a[xx][yy]!='x' && b[xx][yy][z]==-1)
		{
			b[xx][yy][z]=b[x][y][z];
			if (xx==ex && yy==ey)
			{
				cout<<b[xx][yy][z];
				return 0;
			}
			d.push_front((node){xx,yy,z});
		}
		for (int i=1;i<=3;i+=2)
		{
			zz=(z+i)%4;
			if (b[x][y][zz]==-1)
			{
				b[x][y][zz]=b[x][y][z]+1;
				d.push_back((node){x,y,zz});
			}
		}
	}
	cout<<-1;
}