DFS能过吗？我TLE

#include<bits/stdc++.h>
using namespace std;

int n,m,mp[1005][1005],minn=2147483647;
int sx,sy,ex,ey;
bool vis[1005][1005];

int dx[4]={-1,1,0,0};
int dy[4]={0,0,-1,1}; 

bool isin(int x,int y){
	return x>=1&&y>=1&&x<=n&&y<=n;
}

void dfs(int x,int y,int length){
	if(x==ex&&y==ey){
		minn=min(length,minn);
		return;
	}
	for(int i=0;i<4;i++){
		int cx=dx[i]+x;
		int cy=dy[i]+y;
		if(isin(cx,cy)&&!vis[cx][cy]&&!mp[cx][cy]){
			vis[cx][cy]=1;
			length++;
			dfs(cx,cy,length);
			length--;
            vis[cx][cy]=0;
		}
	}
}

int main(){
	cin >> n;
	for(int i=1;i<=n;i++){
		string s;
		cin >> s;
		for(int j=0;j<s.size();j++){
			mp[i][j+1]=s[j]-'0';
		}
	}
	cin >> sx >> sy >> ex >> ey;
	vis[sx][sy]=true;
	dfs(sx,sy,0);
	cout << minn;
	return 0;
}