30pts

#include<bits/stdc++.h>
using namespace std;
const int N=5e5+10;
int n,m,k,ks[N],f[N],ans[N],ns,fs;
bool vis[N],sv[N],t=1;
vector<int> d[N]; 
int fsb(int x){
    return f[x]==x?x:f[x]=fsb(f[x]);
}
void merge(int x,int y){
    if(vis[y])  return ;
    x=fsb(x),y=fsb(y);
    if(x!=y)    ns--;
    f[x]=y;
}
int main(){
    cin>>n>>m;
    while(m--){
        int x,y;
        cin>>x>>y;
        x++;
        y++;
        d[x].push_back(y);
        d[y].push_back(x);
        sv[x]=sv[y]=1;
    }
    cin>>k;
    for(int i=1;i<=k;i++){
        cin>>ks[i];
        ks[i]++;
        vis[ks[i]]=1;
    }
    for(int i=1;i<=n;i++)
        if(!vis[i]){
            f[i]=i;
            ns++;
        }
    ans[k+1]=ns;
    for(int i=k;i;i--){
        int nk=ks[i];
        vis[nk]=0;
        if(!sv[nk]){
            if(t)   ns++;
            ans[i]=ns;
            t=0;
            continue;
        }
        f[nk]=nk;
        ns++;
        for(int j=0;j<d[nk].size();j++)
            merge(nk,d[nk][j]);
        ans[i]=ns;
    }
    for(int i=1;i<=k+1;i++) cout<<ans[i]<<endl;
    return 0;
}

40pts

#include<bits/stdc++.h>
using namespace std;
const int N=5e5+10;
int n,m,k,ks[N],f[N],ans[N],ns,fs;
bool vis[N],sv[N];
vector<int> d[N]; 
int fsb(int x){
    return f[x]==x?x:f[x]=fsb(f[x]);
}
void merge(int x,int y){
    if(vis[y])  return ;
    x=fsb(x),y=fsb(y);
    if(x!=y)    ns--;
    f[x]=y;
}
int main(){
    cin>>n>>m;
    while(m--){
        int x,y;
        cin>>x>>y;
        x++;
        y++;
        d[x].push_back(y);
        d[y].push_back(x);
        sv[x]=sv[y]=1;
    }
    cin>>k;
    for(int i=1;i<=k;i++){
        cin>>ks[i];
        ks[i]++;
        vis[ks[i]]=1;
    }
    for(int i=1;i<=n;i++)
        if(!vis[i]){
            f[i]=i;
            ns++;
        }
    ans[k+1]=ns;
    for(int i=k;i;i--){
        int nk=ks[i];
        if(!sv[nk]){
            ans[i]=++ns;
            continue;
        }
        vis[nk]=0;
        f[nk]=nk;
        ns++;
        for(int j=0;j<d[nk].size();j++)
            merge(nk,d[nk][j]);
        ans[i]=ns;
    }
    for(int i=1;i<=k+1;i++) cout<<ans[i]<<endl;
    return 0;
}