Manthan, Codefest 18 (rated, Div. 1 + Div. 2) (D. Valid BFS?)

Bismillahir Rahmanir Rahim

///Author: Tanvir Ahmmad

///CSE,Islamic University,Bangladesh

#include<iostream>

#include<cstdio>

#include<algorithm>

#include<string>

#include<cstring>

#include<sstream>

#include<cmath>

#include<cstring>

#include<vector>

#include<queue>

#include<map>

#include<set>

#include<stack>

#include<vector>

#include<iterator>

#include <functional> ///sort(arr,arr+n,greater<int>()) for decrement of array

/*every external angle sum=360 degree

  angle find using polygon hand(n) ((n-2)*180)/n*/

///Floor[Log(b)  N] + 1 = the number of digits when any number is represented in base b

using namespace std;

typedef long long ll;

vector<ll>g[200005];

bool vis[200005];

queue<ll>q_t,q;

bool bfs(int node)

{

    q_t.pop();

    q.push(node);

    vis[node]=true;

    while(!q.empty())

    {

        set<ll>st;

        set<ll>::iterator it;

        ll cur=q.front(),cnt=0;

        q.pop();

        for(ll i=0; i<g[cur].size(); i++)

            if(vis[g[cur][i]]==false)

            {

                cnt++;

                vis[g[cur][i]]=true;

                st.insert(g[cur][i]);

            }

            while(cnt--)

            {

                ll piku=q_t.front();

                it=st.find(piku);

                if(vis[piku]==true && it!=st.end()) q.push(piku),q_t.pop();

                else return false;

            }

            st.clear();

    }

    return true;

}

int main()

{

    ios_base::sync_with_stdio(false);

    cin.tie(NULL);

    ll node,a,b,num;

    cin>>node;

    for(ll i=1; i<node; i++)

    {

        cin>>a>>b;

        g[a].push_back(b);

        g[b].push_back(a);

    }

    for(ll i=1; i<=node; i++) cin>>num,q_t.push(num);

    if(bfs(1) && q_t.empty()) cout<<"Yes"<<endl;

    else cout<<"No"<<endl;

    return 0;

}

///Alhamdulillah

Problem Link: https://codeforces.com/problemset/problem/1037/D