1122 Hamiltonian Cycle（25 分）

#include<iostream>
#include<vector>

using namespace std;
vector<vector<int>> vm;
vector<bool> visit;
int main()
{
    int M,N,L,X,a,b,c,a_bef;
    cin >> M>>N;
    vm.resize(M);
    visit.resize(M);
    for (int i = 0; i < N; i++)
    {
        cin >> a >> b;
        a--;
        b--;
        
        vm[a].push_back(b);
        vm[b].push_back(a);
    }


    cin >> L;
    for (int i = 0; i < L; i++)
    {
        fill(visit.begin(), visit.end(), false);
        cin >> X;
        if (X!=M+1)
        {
            while (cin.get()!='\n')
            {
                cin >> c;
            }
            cout << "NO" << endl;
            continue;
        }
        cin >> a;
        a--;
        a_bef = a;
        visit[a] = true;
        bool flag = false;
        for (int j = 1; j < X-1; j++)
        {
            cin >> b;
            b--;
            //没有找到连接线或者访问一个已经访问过的节点
            if((find(vm[a].begin(), vm[a].end(), b)==vm[a].end())||(visit[b]==true))
            {
                while (cin.get()!='\n')//清除后面的数据
                {
                    cin >> c;
                }
                flag = true;
                break;
            }
                visit[b] = true;
                a = b;
        }
        
        if(flag==false)
        {
            cin >> c;
            c--;
            if (c == a_bef) {
                cout << "YES" << endl;
            }
            else
            {
                cout << "NO" << endl;
            }
        }
        else
        {
            cout << "NO" << endl;
        }
    }
    system("pause");
    return 0;
}