两边bfs,先一边找到从1到n的路径并记录下来,然后挨个标记,最后一边bfs找1能到达的点,比较一下就行了
#include<map> #include<set> #include<cmath> #include<queue> #include<stack> #include<vector> #include<cstdio> #include<cassert> #include<iomanip> #include<cstdlib> #include<cstring> #include<iostream> #include<algorithm> #define pi acos(-1) #define ll long long #define mod 1000000007 #define ls l,m,rt<<1 #define rs m+1,r,rt<<1|1 #pragma comment(linker, "/STACK:1024000000,1024000000") using namespace std; const double g=10.0,eps=1e-4; const int N=200000+10,maxn=500+100,inf=0x3f3f3f; vector<int>v[N],p; bool vis[N]; int pre[N],n,res; int color[N]; void bfs(int x) { memset(vis,0,sizeof vis); memset(pre,-1,sizeof pre); queue<int>q; q.push(x); vis[x]=1; while(!q.empty()){ int s=q.front(); q.pop(); for(int i=0;i<v[s].size();i++) { if(!vis[v[s][i]]) { vis[v[s][i]]=1; pre[v[s][i]]=s; q.push(v[s][i]); if(v[s][i]==n)return ; } } } } int bfs1(int x) { memset(vis,0,sizeof vis); queue<int>q; q.push(x); vis[1]=1; int ans=0; while(!q.empty()){ int s=q.front(); // cout<<s<<endl; ans++; q.pop(); for(int i=0;i<v[s].size();i++) { if(color[v[s][i]]==2||vis[v[s][i]])continue; q.push(v[s][i]); vis[v[s][i]]=1; } } return ans; } int main() { ios::sync_with_stdio(false); cin.tie(0); cin>>n; for(int i=2;i<=n;i++) { int a,b; cin>>a>>b; v[a].push_back(b); v[b].push_back(a); } bfs(1); int ans=0; for(int i=pre[n];i!=1;i=pre[i])ans++; ans/=2; memset(color,0,sizeof color); color[1]=1,color[n]=2; for(int i=pre[n];i!=1;i=pre[i]) { if(ans>0)ans--,color[i]=2; else color[i]=1; } // for(int i=1;i<=n;i++)cout<<color[i]<<endl; int res=bfs1(1); if(res>n-res)cout<<"Fennec"<<endl; else cout<<"Snuke"<<endl; return 0; }