bfs

int main()
{
    int t=Int;
    while(t--){
        int n=Int,m=Int;//n=node numbers & m=edges
        vector<int>adj[n+1];
        for(int a=1;a<=m;a++){
            int b=Int,c=Int;
            if(b>c)swap(b,c);
            adj[b].pushv(c);
        }
        int distance[n+1]={0},color[n+1]={white};
        queue<int>bfs;
        bfs.push(1);
        color[1]=grey;
        while(!bfs.empty()){
            int frnt=bfs.front();
            for(int b=0;b<adj[frnt].size();b++){
                int u=frnt,v=adj[frnt][b];
                if(color[v] == white){
                    bfs.push(v);
                    color[v]=grey;
                    distance[v]=distance[u]+1;
                }
            }
            bfs.pop();
        }
    //for(int x=1;x<=n;x++)cout<<"distance of "<<x<<" from 1 is "<<distance[x]<<endl;
    cout<<distance[n]<<endl;
    }
    r0;
}