Brexit Gym - 101490C

题目链接：Brexit

vector的使用（vector存边），巧用queue，相当于Bfs

 /* */
 # include <iostream>
 # include <cstdio>
 # include <cstring>
 # include <string>
 # include <memory>
 # include <cstdlib>
 # include <cmath>
 # include <climits>
 # include <cctype>
 # include <cassert>
 # include <utility>
 # include <deque>
 # include <queue>
 # include <stack>
 # include <vector>
 # include <bitset>
 # include <set>
 # include <map>
 # include <functional>
 # include <algorithm>
 using namespace std;
  
 # define lson l,m,rt<<
 # define rson m+,r,rt<<|
 # define lowbit(x)(x&(-x))
 # define lcm(a,b)(a*b/__gcd(a,b))
 typedef long long ll;
 const ll mod=1e9+;
 const int maxn=2e5+;
 const double eps=1e-;
 const double pi=acos(-1.0);
 int n, m, c, l;
 int de[maxn];
 vector<int>nex[maxn];
 queue<int>qu;
 int flag[maxn];
  
 int main()
 {
     int t;
     while( ~ scanf("%d%d%d%d", &n, &m, &c, &l) )
     {
         for(int i=; i<=n; i++ )
         {
             nex[i].clear();
             de[i]=;
             flag[i]=;
         }
  
         while( !qu.empty() )
             qu.pop();
         for(int i=; i<=m; i++ )
         {
             int u, v;
             scanf("%d%d", &u, &v);
             nex[u].push_back(v);
             nex[v].push_back(u);
             de[u]++;
             de[v]++;
         }
  
         flag[l]=;
         qu.push(l);
         while( !qu.empty() )
         {
             int cur=qu.front();
             qu.pop();
             for(int i=; i<nex[cur].size(); i++ )
             {
                 de[nex[cur][i]]--;
                 if(  de[nex[cur][i]]<=nex[nex[cur][i]].size()/ && flag[nex[cur][i]]== )
                 {
                     flag[nex[cur][i]] = ;//避免重复入栈
                     qu.push(nex[cur][i]);
                 }
             }
         }
         if( flag[c]== )
             cout<<"leave"<<endl;
         else
             cout<<"stay"<<endl;
     }
     return ;
 }