#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define N 200010
ll n,m;
bool vis[N];
deque<ll>q[N];
vector<ll>e[N];
ll ans[N];
ll xu[N],cn;
inline bool cmp(ll x,ll y){
	vector<ll>tem1,tem2;
	while(!q[x].empty()&&!q[y].empty()){
		ll s=q[x].front(),t=q[y].front();tem1.push_back(s);tem2.push_back(t);q[x].pop_front();q[y].pop_front();
		if(s!=t){
			for(int i=tem1.size()-1;i>=0;i--)q[x].push_front(tem1[i]);
			for(int i=tem2.size()-1;i>=0;i--)q[y].push_front(tem2[i]);
			return s<=t;
		}
	}
	for(int i=tem1.size()-1;i>=0;i--)q[x].push_front(tem1[i]);
	for(int i=tem2.size()-1;i>=0;i--)q[y].push_front(tem2[i]);
	if(q[x].size()!=q[y].size())return q[x].size()>q[y].size();
	return x<y;
}
inline void dfs(ll x){
	for(auto o:e[x])dfs(o);
	cn=0;for(auto o:e[x])xu[++cn]=o;
	sort(xu+1,xu+cn+1,cmp);
	if(vis[x])q[x].push_back(-1);
	for(int i=1;i<=cn;i++){
		ans[xu[i]]=i-1;
		q[x].push_back(0);q[xu[i]].push_back(1);
		if(q[x].size()<q[xu[i]].size()){
			swap(q[x],q[xu[i]]);
			while(!q[xu[i]].empty()){
				ll o=q[xu[i]].back();q[xu[i]].pop_back();
				q[x].push_front(o);
			}
		}else{
			while(!q[xu[i]].empty()){
				ll o=q[xu[i]].front();q[xu[i]].pop_front();
				q[x].push_back(o);
			}
		}
	}
	return ;
}
int main()
{
//	freopen("test1.in","r",stdin);
	//freopen(".in","r",stdin);
	//freopen("test1.out","w",stdout);
	ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
	ll ti;cin>>ti;while(ti--){
		for(int i=0;i<=n;i++)e[i].clear(),vis[i]=0,q[i].clear();
		cin>>n>>m;for(int i=1,x;i<=n;i++)cin>>x,e[x].push_back(i); 
		for(int i=1,x;i<=m;i++)cin>>x,vis[x]=1; 
		dfs(0);
		for(int i=1;i<=n;i++)cout<<((char)(ans[i]+'a'));
		cout<<'\n';
	}return 0;
}