Shortest Route using BFS

#include<bits/stdc++.h>
 
using namespace std;
 
#define ll long long 
#define scn(n) scanf("%d",&n)
#define lscn(n) scanf("%lld",&n)
#define lpri(n) printf("%lld",n)
#define pri(n) printf("%d",n)
#define pln() printf("\n")
#define priln(n) printf("%d\n",n)
#define lpriln(n) printf("%lld\n",n)
#define fr(i,init,n) for(int i=init;i<n;i++)
#define pb push_back     
#define mp make_pair
#define F first
#define S second
#define gcd __gcd
#define inf INT_MAX
#define ninf INT_MIN
#define f(v,value) find(v.begin(),v.end(),value)
#define asc(a,n) sort(a,a+n)
#define desc(a,n,data_type) sort(a,a+n,greater<data_type>())
#define vasc(v)  sort(v.begin(),v.end())
#define vdesc(v,data_type) sort(v.begin(),v.end(),greater<data_type>())
const int mod = 1e9 + 7;         
const int N = 1e5 + 4;
 
int nooffac(long long a)
{
int c=0;
for(int i=1;i*i<=a;i++)
{
if(a%i==0)
{
c++;
if(a/i!=i)
c++;
}
return c;
}
}
 
ll check(ll val)
{
    ll k2=val;ll t=0;ll sum=0;
    val=val-val%5;
    while(k2>0)
    { 
        k2=k2/5;
         t++;
        //cout<<"k2"<<k2;
    }
    t--;//cout<<t<<" ";
     ll k1=pow(5,t);
     //cout<<k1;
    while(k1>=5)
    {
        
    
        
        sum+=val/k1;
 
        k1=k1/5;
        //cout<<sum<<"@ "<<k1;
        
    }
    //cout<<val<<"sum"<<sum<<" ";
    return sum;
}
 
ll bi_search(ll k)
{
    ll low=0;
    ll high=1e12;
    ll pos;
    while(high>low)
    {
        
        ll mid=(low+high)/2;
        //cout<<"mid"<<mid<<" ";
        if(check(mid)>=k)
        {
            pos=mid; //cout<<pos<<" ";
            high=mid-1;
        }
        else
        low=mid+1;
    }
   return pos;
}
int main()
{
   
   ll n1;
   lscn(n1);
   fr(i,0,n1)
   {
   
   ll n;
   lscn(n);
   ll m;
   lscn(m);
   queue<ll>q,q1;
   vector<ll>adj[n+1];
   fr(i,0,m)
   {
    ll a;ll b;
	lscn(a);lscn(b);
	adj[a].pb(b);
	adj[b].pb(a);
   }  

   ll vis[n+1]={0};
   q.push(1);ll k=0;ll c=0;vis[1]=1;
   while(!q.empty())
   {
	   ll x=q.front();
	 
	   q.pop();
	   
	   for(auto child:adj[x])
	   {
		   
		 
		   if(vis[child]==0)
		   {
			   vis[child]=1;
		        q1.push(child);
		        
		   }
	   }
	     
		   if(q.size()==0)
		   {
			   c++;
			   while(!q1.empty())
			   {
				   ll x=q1.front();
				   if(x==n)
				   {
					   c++;
					   k=1;
					   break;
				   }
				   q1.pop();
				   q.push(x);
			   }
		   }
		   if(k==1)
		   break;
   }
   cout<<--c<<endl;
}}