为什么会爆内存呢

#include<bits/stdc++.h>
using namespace std;
const int maxn=1000;
struct fl{
	int floor,d;
};
queue<fl> q;
int n,a,b;
int k[maxn],vis[maxn];
int main(){
	cin>>n>>a>>b;
	for(int i=1;i<=n;i++){
		cin>>k[i];
	}
	q.push((fl){a,0});
	vis[a]=1;
	fl now;
	while(!q.empty()){
		now=q.front();
		q.pop();
		if(now.floor==b){
			break;
		}
		for(int i=-1;i<=1;i+=2){
			int ft=now.floor+k[now.floor]*i;
			if(ft>=1&&ft<=n&&vis[ft]==0){
				q.push((fl){ft,now.d+1});
				vis[ft]==1;
			}
		}
	}
	if(now.floor==b){
		cout<<now.d;
	}
	else {
		cout<<-1<<"\n";
	}
	return 0;
}