hdu2460 和 poj3694

poj3694:先预处理出询问边（u，v）的最小公共祖先lca{u,v}（用tarjan的lca离线算法）和桥的总数scc，最后每次从u到lca{u,v},v到lca{u,v}，找出其中桥的数量，用scc减去，就是答案了。因为每次形成了圈，所以用并查集缩点，不然会TLE；写了一天就T在这儿了。




hdu2460:尼玛啊？hdu太坑爹了，个种深搜都不行啊？ 连并查集路径压缩 的深搜都不行 害我改了一晚上…各种RE啊？其它和poj3694一样。





//poj3694 代码：

#include<iostream>

#include<cstdio>

#include<cstring>

#include<algorithm>

#define INF 100005

#define maxc 400005

usingnamespace std;

structnode

{

    inte,next;

}edge[maxc],Tedge[2005];

structnode1

{

    inta,b;

}qurey[1005],fa[INF];

intnum,top,scc,bleg[INF],st[INF],first1[INF],first[INF],dfn[INF],low[INF],blegs[INF];

intused[INF],edges[maxc],ancestor[INF],lca[2005],ids[maxc],fids[maxc],ids1[maxc],fids1[maxc];

intFind(intx)

{

    returnbleg[x]==x?x:bleg[x]=Find(bleg[x]);

}

voidUnion(inta,intb)

{

    a=Find(a),b=Find(b);

    bleg[b]=a;

}

intFinds(intx)

{

    returnblegs[x]==x?x:blegs[x]=Finds(blegs[x]);

}

voidUnions(inta,intb)

{

    a=Finds(a),b=Finds(b);

    blegs[a]=b;

}

voidtarjan(intv)

{

    dfn[v]=low[v]=++num;

    st[++top]=v;

    ancestor[Find(v)]=v;

    for(inti=first[v];i!=-1;i=edge[i].next)

    {

        intu=edge[i].e;

        if(fids[ids[i]])

        continue;

        fids[ids[i]]=1;

        if(!dfn[u])

        {

            fa[u].a=v,fa[u].b=i;

            tarjan(u);

            Union(v,u);

            ancestor[Find(v)]=v;

            low[v]=min(low[v],low[u]);

            if(low[u]>dfn[v])

            {

                scc++;

                edges[ids[i]]=1;

                while(true)

                {

                    intx=st[top--];

                    if(x==u)

                    break;

                }

            }

        }

        else

        low[v]=min(low[v],dfn[u]);

    }

    used[v]=1;

    for(inti=first1[v];i!=-1;i=Tedge[i].next)

    if(used[Tedge[i].e] && !fids1[ids1[i]])

    {

        lca[ids1[i]]=ancestor[Find(Tedge[i].e)];

        fids1[ids1[i]]=1;

    }

}

intmain()

{

    intn,m,q,cas=0;

    while(scanf("%d%d",&n,&m),m+n)

    {

        cas++;

        memset(first,-1,sizeof(first));

        memset(first1,-1,sizeof(first1));

        memset(dfn,0,sizeof(dfn));

        memset(edges,0,sizeof(edges));

        memset(fids,0,sizeof(fids));

        memset(fids1,0,sizeof(fids1));

        memset(used,0,sizeof(used));

        inta,b,nume,number;

        number=nume=top=scc=num=0;

        for(inti=1;i<=n;i++)

        blegs[i]=fa[i].a=bleg[i]=i;

        while(m--)

        {

            scanf("%d%d",&a,&b);

            ids[nume]=number;

            edge[nume].e=b,edge[nume].next=first[a],first[a]=nume++;

            ids[nume]=number++;

            edge[nume].e=a,edge[nume].next=first[b],first[b]=nume++;

        }

        number=nume=0;

        scanf("%d",&q);

        for(inti=0;i<q;i++)

        {

            scanf("%d%d",&a,&b);

            qurey[i].a=a,qurey[i].b=b;

            ids1[nume]=number;

            Tedge[nume].e=b,Tedge[nume].next=first1[a],first1[a]=nume++;

            ids1[nume]=number++;

            Tedge[nume].e=a,Tedge[nume].next=first1[b],first1[b]=nume++;

        }

        tarjan(1);

        printf("Case %d:n",cas);

        for(inti=0;i<q;i++)

        {

            if(scc!=0)

            {

                for(intk=qurey[i].a,j=Finds(fa[k].a);j!=Finds(qurey[i].a);k=j,j=Finds(fa[j].a))

                {

                    Unions(qurey[i].a,j);

                    if(edges[ids[fa[k].b]])

                    {

                        scc--;

                        edges[ids[fa[k].b]]=0;

                    }

                    if(j==Find(lca[i]))

                    break;

                }

                for(intk=qurey[i].b,j=Finds(fa[k].a);j!=Finds(qurey[i].b);k=j,j=Finds(fa[j].a))

                {

                    Unions(qurey[i].b,j);

                    if(edges[ids[fa[k].b]])

                    {

                        scc--;

                        edges[ids[fa[k].b]]=0;

                    }

                    if(j==Finds(lca[i]))

                    break;

                }

                Union(qurey[i].a,qurey[i].b);

            }

            printf("%dn",scc);

        }

        printf("n");

    }

    return0;

}

 

//hdu2460  代码：

#include<iostream>

#include<cstdio>

#include<cstring>

#include<algorithm>

#define INF 100005

#define maxc 400005

usingnamespace std;

structnode

{

    inte,next;

}edge[maxc],Tedge[2005];

structnode1

{

    inta,b;

}qurey[1005],fa[INF];

intnum,top,scc,bleg[INF],st[INF],first1[INF],first[INF],dfn[INF],low[INF],blegs[INF],vis[INF];

intused[INF],edges[maxc],ancestor[INF],lca[2005],ids[maxc],fids[maxc],ids1[maxc],fids1[maxc];

intFind(intx)

{

    inty=x;

    while(y!=bleg[y])

    y=bleg[y];

    while(x!=bleg[x])

    {

        intpx=bleg[x];

        bleg[x]=y;

        x=px;

    }

    returny;

}

voidUnion(inta,intb)

{

    a=Find(a),b=Find(b);

    bleg[b]=a;

}

intFinds(intx)

{

    inty=x;

    while(y!=blegs[y])

    y=blegs[y];

    while(x!=blegs[x])

    {

        intpx=blegs[x];

        blegs[x]=y;

        x=px;

    }

    returny;

}

voidUnions(inta,intb)

{

    a=Finds(a),b=Finds(b);

    blegs[a]=b;

}

voidtarjan(intv)

{

    st[++top]=v;

    while(top)

    {

        v=st[top];

        if(!vis[v])

        dfn[v]=low[v]=++num,vis[v]=1;

        ancestor[Find(v)]=v;

        inti;

        for(i=first[v];i!=-1;i=edge[i].next)

        {

            intu=edge[i].e;

            if(fids[ids[i]])

            continue;

            fids[ids[i]]=1;

            if(!vis[u])

            {

                fa[u].a=v,fa[u].b=i;

                break;

            }

            elseif(vis[u]==1)

            low[v]=min(low[v],dfn[u]);

        }

        if(i==-1 && top>1)

        {

            Union(st[top-1],v);

            low[st[top-1]]=min(low[st[top-1]],low[v]);

            if(low[v]>dfn[st[top-1]])

            {

                scc++;

                edges[ids[fa[v].b]]=1;

            }

        }

        if(i==-1)

        {

            vis[v]=2;

            top--;

            used[v]=1;

            for(i=first1[v];i!=-1;i=Tedge[i].next)

            if(used[Tedge[i].e] && !fids1[ids1[i]])

            {

                lca[ids1[i]]=ancestor[Find(Tedge[i].e)];

                fids1[ids1[i]]=1;

            }

        }

        else

        st[++top]=edge[i].e;

    }

}

intmain()

{

    intn,m,q,cas=0;

    while(scanf("%d%d",&n,&m),m+n)

    {

        cas++;

        memset(first,-1,sizeof(first));

        memset(first1,-1,sizeof(first1));

        memset(dfn,0,sizeof(dfn));

        memset(edges,0,sizeof(edges));

        memset(fids,0,sizeof(fids));

        memset(fids1,0,sizeof(fids1));

        memset(used,0,sizeof(used));

        memset(vis,0,sizeof(vis));

        inta,b,nume,number;

        number=nume=top=scc=num=0;

        for(inti=1;i<=n;i++)

        blegs[i]=fa[i].a=bleg[i]=i;

        while(m--)

        {

            scanf("%d%d",&a,&b);

            ids[nume]=number;

            edge[nume].e=b,edge[nume].next=first[a],first[a]=nume++;

            ids[nume]=number++;

            edge[nume].e=a,edge[nume].next=first[b],first[b]=nume++;

        }

        number=nume=0;

        scanf("%d",&q);

        for(inti=0;i<q;i++)

        {

            scanf("%d%d",&a,&b);

            qurey[i].a=a,qurey[i].b=b;

            ids1[nume]=number;

            Tedge[nume].e=b,Tedge[nume].next=first1[a],first1[a]=nume++;

            ids1[nume]=number++;

            Tedge[nume].e=a,Tedge[nume].next=first1[b],first1[b]=nume++;

        }

        tarjan(1);

        printf("Case %d:n",cas);

        for(inti=0;i<q;i++)

        {

            if(scc!=0)

            {

                for(intk=qurey[i].a,j=Finds(fa[k].a);j!=Finds(qurey[i].a);k=j,j=Finds(fa[j].a))

                {

                    Unions(qurey[i].a,j);

                    if(edges[ids[fa[k].b]])

                    {

                        scc--;

                        edges[ids[fa[k].b]]=0;

                    }

                    if(j==Find(lca[i]))

                    break;

                }

                for(intk=qurey[i].b,j=Finds(fa[k].a);j!=Finds(qurey[i].b);k=j,j=Finds(fa[j].a))

                {

                    Unions(qurey[i].b,j);

                    if(edges[ids[fa[k].b]])

                    {

                        scc--;

                        edges[ids[fa[k].b]]=0;

                    }

                    if(j==Finds(lca[i]))

                    break;

                }

                Union(qurey[i].a,qurey[i].b);

            }

            printf("%dn",scc);

        }

        printf("n");

    }

    return0;

}