Brexit Gym - 101490C

 1 /* */
 2 # include <iostream>
 3 # include <cstdio>
 4 # include <cstring>
 5 # include <string>
 6 # include <memory>
 7 # include <cstdlib>
 8 # include <cmath>
 9 # include <climits>
10 # include <cctype>
11 # include <cassert>
12 # include <utility>
13 # include <deque>
14 # include <queue>
15 # include <stack>
16 # include <vector>
17 # include <bitset>
18 # include <set>
19 # include <map>
20 # include <functional>
21 # include <algorithm>
22 using namespace std;
23  
24 # define lson l,m,rt<<1
25 # define rson m+1,r,rt<<1|1
26 # define lowbit(x)(x&(-x))
27 # define lcm(a,b)(a*b/__gcd(a,b))
28 typedef long long ll;
29 const ll mod=1e9+7;
30 const int maxn=2e5+10;
31 const double eps=1e-18;
32 const double pi=acos(-1.0);
33 int n, m, c, l;
34 int de[maxn];
35 vector<int>nex[maxn];
36 queue<int>qu;
37 int flag[maxn];
38  
39 int main()
40 {
41     int t;
42     while( ~ scanf("%d%d%d%d", &n, &m, &c, &l) )
43     {
44         for(int i=1; i<=n; i++ )
45         {
46             nex[i].clear();
47             de[i]=0;
48             flag[i]=0;
49         }
50  
51         while( !qu.empty() )
52             qu.pop();
53         for(int i=1; i<=m; i++ )
54         {
55             int u, v;
56             scanf("%d%d", &u, &v);
57             nex[u].push_back(v);
58             nex[v].push_back(u);
59             de[u]++;
60             de[v]++;
61         }
62  
63         flag[l]=1;
64         qu.push(l);
65         while( !qu.empty() )
66         {
67             int cur=qu.front();
68             qu.pop();
69             for(int i=0; i<nex[cur].size(); i++ )
70             {
71                 de[nex[cur][i]]--;
72                 if(  de[nex[cur][i]]<=nex[nex[cur][i]].size()/2 && flag[nex[cur][i]]==0 )
73                 {
74                     flag[nex[cur][i]] = 1;//避免重复入栈
75                     qu.push(nex[cur][i]);
76                 }
77             }
78         }
79         if( flag[c]==1 )
80             cout<<"leave"<<endl;
81         else
82             cout<<"stay"<<endl;
83     }
84     return 0;
85 }