[51nod1299]监狱逃离

到现在还是不会写系列，直接贴题解了。

http://www.51nod.com/question/index.html#!questionId=1157

 #include<cstdio>
 #include<iostream>
 #include<cstring>
 #include<algorithm>
 #include<queue>
 #define ll long long
 #define ui unsigned int
 using namespace std;
 const int maxn=;
 struct zs{int too,pre;}e[maxn<<];int tot,last[maxn];
 int zt[maxn],deg[maxn];
 int i,j,k,n,m,ans;
 bool gg[maxn],GG;

 int ra,fh;char rx;
 inline int read(){
     rx=getchar(),ra=,fh=;
     while((rx<''||rx>'')&&rx!='-')rx=getchar();
     if(rx=='-')fh=-,rx=getchar();
     while(rx>=''&&rx<='')ra*=,ra+=rx-,rx=getchar();return ra*fh;
 }
 inline void insert(int a,int b){
     deg[a]++,deg[b]++;
     e[++tot].too=b,e[tot].pre=last[a],last[a]=tot,
     e[++tot].too=a,e[tot].pre=last[b],last[b]=tot;
 }
 void dfs(int x,int fa){
     zt[x]=;
     int num[]={,,};
     for(int i=last[x];i;i=e[i].pre)if(e[i].too!=fa)
         dfs(e[i].too,x),num[zt[e[i].too]]++;
     if(gg[x]&&deg[x]==)GG=;
     if(gg[x])zt[x]=,ans+=num[];
     else if(num[]&&num[])zt[x]=,ans++;
     else if(num[]||num[])zt[x]=num[]?:;
     else if(num[])zt[x]=;
 //    printf("x:%d   zt:%d\n",x,zt[x]);
 }
 int main(){
     n=read()+,m=read();
     for(i=;i<n;i++)insert(read()+,read()+);
     for(i=;i<=m;i++)gg[read()+]=;
     for(i=n;i;i--)if(deg[i]==){dfs(i,),ans+=zt[i]==;break;}
     printf("%d\n",!GG?ans:-);
 }