双端队列BFS模板题求助！

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
struct node{
	int x,y;
	node(int xx,int yy) {
		x = xx;
		y = yy;
		return;
	}
};
int n,m,dx[4] = {-1,-1,1,1},dy[4] = {-1,1,-1,1},cdx[4] = {0,0,1,1},cdy[4] = {0,1,0,1};
ll dis[510][510];
char g[510][510],dir[4] = {'\\','/','/','\\'};
deque<node> q;
void bfs() {
	memset(dis,0x3f,sizeof(dis));
	q.push_back(node(0,0));
	dis[0][0] = 0;
	while (!q.empty()) {
		int ux = q.front().x,uy = q.front().y;
		q.pop_front();
		for (int i = 0;i < 4;i ++) {
			int vx = ux + dx[i],vy = ux + dy[i];
			if (vx >= 0 && vx <= n && vy >= 0 && vy <= m) {
				int w = g[ux + cdx[i]][uy + cdy[i]] != dir[i];
				if (dis[vx][vy] > dis[ux][uy] + w) {
					dis[vx][vy] = dis[ux][uy] + w;
					if (w) q.push_back(node(vx,vy));
					else q.push_front(node(vx,vy));
					if (vx == n && vy == m) break;
				}
			}
		}
	}
	return;
}
int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cin >> n >> m;
	for (int i = 1;i <= n;i ++)
		for (int j = 1;j <= m;j ++)
			cin >> g[i][j];
	bfs();
//	for (int i = 0;i <= n;i ++) {
//		for (int j = 0;j <= m;j ++)
//			if (dis[i][j] >= 0x3f3f3f3f3f3f3f3fll) cout << "inf\t";
//			else cout << dis[i][j] << "\t";
//		cout << "\n";
//	}
	if (dis[n][m] >= 0x3f3f3f3f3f3f3f3fll) cout << "NO SOLUTION\n";
	else cout << dis[n][m] << "\n";
	return 0;
}