[Luogu 1197] JSOI2008 星球大战

<题目链接>

#include <cstdio>
#include <cstring>
const int MAXN=400010,MAXM=200010;
bool gone[MAXN];
int n,m,k,sum,q[MAXN],ans[MAXN];
struct Edge
{
    int to;
    Edge *next;
    Edge(int to,Edge* next):to(to),next(next){}
    ~Edge(void)
    {
        if(next!=nullptr)
            delete next;
    }
}*head[MAXN];
class UFS
{
    private:
        bool exist[MAXN];
        int f[MAXN];
        int Find(int x)
        {
            return x==f[x] ? x : f[x]=Find(f[x]);
        }
    public:
        UFS(int n)
        {
            memset(exist,0,sizeof exist);
            for(int i=0;i<n;++i)
            {
                head[i]=nullptr;
                f[i]=i;
            }
        }
        ~UFS(void)
        {
            for(int i=0;i<n;++i)
                delete head[i];
        }
        void Merge(int x,int y)
        {
            f[Find(y)]=Find(x);
        }
        int Count(void)
        {
            int ans=0;
            for(int i=0,t;i<n;++i)
                if(!gone[i] && !exist[t=Find(i)])
                {
                    ++ans;
                    exist[t]=1;
                }
            return ans;
        }
        bool Connected(int x,int y)
        {
            return Find(x)==Find(y);
        }
};
void AddEdges(int u,int v)
{
    head[u]=new Edge(v,head[u]);
    head[v]=new Edge(u,head[v]);
}
int main(int argc,char** argv)
{
    scanf("%d %d",&n,&m);
    static UFS *S=new UFS(n);
    for(int i=1,x,y;i<=m;++i)
    {
        scanf("%d %d",&x,&y);
        AddEdges(x,y);
    }
    scanf("%d",&k);
    for(int i=1;i<=k;++i)
    {
        scanf("%d",&q[i]);
        gone[q[i]]=true;
    }
    for(int u=0;u<n;++u)
        if(!gone[u])
            for(Edge *i=head[u];i!=nullptr;i=i->next)
            {
                int v=i->to;
                if(!gone[v])
                    S->Merge(u,v);
            }
    ans[k]=sum=S->Count();
    for(int j=k,u;j>=1;--j)
    {
        ++sum;
        gone[u=q[j]]=false;
        for(Edge *i=head[u];i!=nullptr;i=i->next)
        {
            int v=i->to;
            if(gone[v]==false && !S->Connected(u,v))
            {
                --sum;
                S->Merge(u,v);
            }
        }
        ans[j-1]=sum;
    }
    for(int i=0;i<=k;++i)
        printf("%d\n",ans[i]);
    delete S;
    return 0;
}

谢谢阅读。

原文地址：https://www.cnblogs.com/Capella/p/9130807.html