【PAT】1121. Damn Single

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <string>
#include <vector>
#include <map>
#include <set>
#include <queue>
#include <stack>
#define FOR(i, x, y) for(int i = x; i <= y; i++)
#define rFOR(i, x, y) for(int i = x; i >= y; i--)
#define MAXN 100100
#define oo 0x3f3f3f3f
using namespace std;

int h[MAXN];
int hh[MAXN];
int a[MAXN];
int aa[MAXN];
int main()
{
#ifdef LOCAL
freopen("data.in","r",stdin);
freopen("data.out","w",stdout);
#endif // LOCAL

int n;
cin>>n;
map<int,int> mp,pm;
FOR(i,1,n){
int a,b;
cin>>a>>b;
mp[a]=b;mp[b]=a;

}
int m;
cin>>m;
FOR(i,0,m-1)
{
cin>>a[i];
hh[a[i]]=1;
}
int cnt=0;
FOR(i,0,m-1)
{

if(mp.find(a[i])==mp.end()){
aa[cnt++]=a[i];
}else{
int id=mp[a[i]];
if(hh[id]==0)
aa[cnt++]=a[i];
}

}
sort(aa,aa+cnt);
cout<<cnt<<endl;
FOR(i,0,cnt-1)
{
printf("%05d",aa[i]);
if(i!=cnt-1)printf(" ");
}
return 0;
}