HDU1272 小希的迷宫

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1272

#include<iostream>
using namespace std;

const int MAX_VETEX_NUM = 100001;
bool flag[MAX_VETEX_NUM];
int connectedList[MAX_VETEX_NUM];
bool isOk = true;
int nStart,nEnd;

void initConnectedList()
{
    for (int i = 0; i < MAX_VETEX_NUM; ++i)
    {
        connectedList[i] = i;
        flag[i] = false;
    }
}
int findInConnectList(int vetex)
{
    int pos = vetex;
    while(pos != connectedList[pos])
       {
        pos = connectedList[pos];
    }
    return pos;
}
int countListNum()
{
    int count = 0;
    for (int i = 0; i < MAX_VETEX_NUM; ++i)
    {
        if (flag[i] == true)
        {
            if (findInConnectList(i) == i)
            {
                ++count;
            }
        }
    }
    return count;
}

void process()
{
    if( findInConnectList(nStart) == findInConnectList(nEnd))
    {
           isOk = false;
           return;
    }
    if( findInConnectList(nStart) == nStart && findInConnectList(nEnd) == nEnd)
       {
        connectedList[nEnd] = nStart;
    }
    else if(findInConnectList(nStart) == nStart)
       {
        connectedList[nStart] = findInConnectList(nEnd);
    }
    else
       {
        connectedList[nEnd] = findInConnectList(nStart);
    }
    flag[nStart] = true;
    flag[nEnd] = true;
}
int main()
{
    while(cin >> nStart >> nEnd)
    {
           if(nStart == -1 && nEnd == -1) break;
           if(nStart || nEnd)
           {
            isOk = true;
            memset(flag, false ,sizeof(flag));
            initConnectedList();
            process();
            while(cin >> nStart >> nEnd,nStart || nEnd)
            {
               if(isOk == true)
               {
                   process();
               }
               }
            if(isOk == true) // 如果没有回环,也有可能在不同连通分量中
            {
                int count = 0;
                count = countListNum();
                 if(count>1)
                  {
                    isOk = false;
                }
            }
           }
           else
           {
            isOk = true;
           }
           if(isOk == false)
        {
            cout << "No" << endl;
        }
           else
        {
            cout << "Yes" << endl;
        }
    }
    return 0;
}