BZOJ[1969] [Ahoi2005]LANE 航线规划

这个题很清真

就是可以考虑将删除的边倒叙插入，因为题面中说了，保证删了所有边之后，保证图的连通性 ，所以先在删完点的图上缩点，然后剩下的边就是关键边，之后再把删除的边插入，这样就会使得之前的一些点之间的关键边的不关键，之后用线段树维护就行了

#include <set>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <algorithm>
# define maxM 100010
# define maxn 30010
# define MP make_pair
# define X first
# define Y second
using namespace std;
void ot(){cout<<"***"<<endl;}
void fen(){cout<<"-------------"<<endl;}
typedef pair<int,int> Pi;
int n,m;
struct LINK{    
    struct node{
        int u,v,nxt;
    }g[2*maxM];
    int adj[maxn],e;
    void add(int u,int v){
        g[e]=(node){u,v,adj[u]};
        adj[u]=e++;
    }
    LINK(){memset(adj,-1,sizeof(adj)); e=0;}
}A,B;
Pi bi[maxM];
bool cmp(const Pi a,const Pi b){
    if(a.X==b.X) return a.Y<b.Y;
    return a.X<b.X;
}
struct QQ{
    int od,u,v,ans;
}Q[maxM];
int tip;
void init(){
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;i++){
        scanf("%d%d",&bi[i].X,&bi[i].Y);
        if(bi[i].X>bi[i].Y) swap(bi[i].X,bi[i].Y);
//        cout<<bi[i].X<<"  "<<bi[i].Y<<endl;
    }
//    ot(); exit(0);
    sort(bi+1,bi+m+1,cmp);
    int x,y,z;
    while(1){
        scanf("%d",&x); if(x==-1) break;
        Q[++tip].od=x;  scanf("%d%d",&Q[tip].u,&Q[tip].v);
        if(Q[tip].u>Q[tip].v) swap(Q[tip].u,Q[tip].v);
//        cout<<"x=="<<x<<"  "<<Q[tip].u<<"  "<<Q[tip].v<<endl;
    }
}
bool operator < (const Pi a,const Pi b){
    if(a.X==b.X) return a.Y<b.Y;
    return a.X<b.X;
}
bool pd[maxM];
void Del_lk(){
    int pos;
    for(int i=1;i<=tip;i++){
        if(Q[i].od) continue;
        pos=lower_bound(bi+1,bi+m+1,MP(Q[i].u,Q[i].v) )-bi;
        pd[pos]=1;
    }
    for(int i=1;i<=m;i++){
        if(pd[i]) continue;
        A.add(bi[i].X,bi[i].Y); A.add(bi[i].Y,bi[i].X);
    }
}
int dfn[maxn],low[maxn],stack[maxn],belong[maxn],cnt,stp,head;
bool instack[maxn];
void tarjan(int x,int fa){
    dfn[x]=low[x]=++stp; stack[++head]=x; instack[x]=1;
    for(int i=A.adj[x];i!=-1;i=A.g[i].nxt){
        int v=A.g[i].v; if(v==fa) continue;
        if(dfn[v]==-1){
            tarjan(v,x); low[x]=min(low[x],low[v]);
        }
        else if(instack[v]) low[x]=min(low[x],dfn[v]);
    }
    if(low[x]==dfn[x]){
        int tmp; cnt++;
        while(1){
            tmp=stack[head--];
            instack[tmp]=0;
            belong[tmp]=cnt;
            if(x==tmp) break;
        }
    }
}
int fa[maxn],dep[maxn],size[maxn],son[maxn];
void dfs1(int x){
    size[x]=1;
    for(int i=B.adj[x];i!=-1;i=B.g[i].nxt){
        int v=B.g[i].v; if(v==fa[x]) continue;
        dep[v]=dep[x]+1; fa[v]=x; 
        dfs1(v);
        size[x]+=size[v];
        if(size[son[x]] < size[v]) son[x]=v;
    }
}
int top[maxn],id[maxn],Pos[maxn];
void dfs2(int x,int tp){
    top[x]=tp; Pos[x]=++stp; id[stp]=x; 
    if(son[x]) dfs2(son[x],tp);
    for(int i=B.adj[x];i!=-1;i=B.g[i].nxt){
        int v=B.g[i].v; if(v==fa[x] || v==son[x]) continue;
        dfs2(v,v);
    }
}
int sum[4*maxn],mk[4*maxn];
void pushup(int now){
    sum[now]=sum[now<<1]+sum[now<<1|1];
}
void pushdown(int now,int l,int r,int mid){
    if(mk[now]==-1) return;
    int ls=now<<1,rs=now<<1|1;
    sum[ls]=mk[now]*(mid-l+1); mk[ls]=mk[now];
    sum[rs]=mk[now]*(r-mid); mk[rs]=mk[now];
    mk[now]=-1;
}
void upd(int left,int right,int now,int l,int r,int num){
    if(left<=l && r<=right){
        sum[now]=num*(r-l+1); mk[now]=num; return;
    }
    int mid=(l+r)>>1;
    pushdown(now,l,r,mid);
    if(left<=mid) upd(left,right,now<<1,l,mid,num);
    if(right>mid) upd(left,right,now<<1|1,mid+1,r,num);
    pushup(now);
}
int query(int left,int right,int now,int l,int r){
    if(left<=l && r<=right) return sum[now];
    int mid=(l+r)>>1;
    pushdown(now,l,r,mid);
    int ret=0;
    if(left<=mid) ret+=query(left,right,now<<1,l,mid);
    if(right>mid) ret+=query(left,right,now<<1|1,mid+1,r);
    return ret;
}
void change(int x,int y){
    int tx=top[x],ty=top[y];
    int ret=0;
    while(tx^ty){
        if(dep[tx]<dep[ty]) swap(tx,ty),swap(x,y);
        upd(Pos[tx],Pos[x],1,1,stp,0);
        x=fa[tx]; tx=top[x];
    }
    if(dep[x]>dep[y]) swap(x,y);
    if(Pos[y]>Pos[x]) upd(Pos[x]+1,Pos[y],1,1,stp,0);
}
int find(int x,int y){
    int tx=top[x],ty=top[y];
    int ret=0;
    while(tx^ty){
        if(dep[tx]<dep[ty]) swap(tx,ty),swap(x,y);
        ret+=query(Pos[tx],Pos[x],1,1,stp);
        x=fa[tx]; tx=top[x];
    }
    if(dep[x]>dep[y]) swap(x,y);
    if(Pos[y]>Pos[x]) ret+=query(Pos[x]+1,Pos[y],1,1,stp);
    return ret;
}
void check1(){
    for(int i=1;i<=n;i++){
        cout<<"i= "<<i<<"  "<<belong[i]<<endl;
    } cout<<endl;
//    cout<<cnt<<"   "<<stp<<endl;
    for(int i=1;i<=cnt;i++){
        cout<<"i=  "<<i<<"  "<<dep[i]<<"  "<<fa[i]<<"  "<<Pos[i]<<endl;
    }
}
void work(){
    memset(dfn,-1,sizeof(dfn));
    memset(mk,-1,sizeof(mk));
    tarjan(1,-1);
    for(int i=0;i<A.e;i++){
        int u=A.g[i].u, v=A.g[i].v;
        if(belong[u]!=belong[v]){
            B.add(belong[u],belong[v]);
        }
    }
    stp=0;
    dfs1(1); dfs2(1,1);
//    check1();
    upd(2,stp,1,1,stp,1);
    for(int i=tip;i>=1;i--){
//        cout<<"i=="<<i<<endl;
        if(Q[i].od){
            if(belong[Q[i].u]==belong[Q[i].v]){
                Q[i].ans=0; continue;
            }
//            cout<<belong[Q[i].u]<<"  "<<belong[Q[i].v]<<endl;
            Q[i].ans=find(belong[Q[i].u],belong[Q[i].v]);
        }
        else{
            if(belong[Q[i].u]==belong[Q[i].v]) continue;
            change(belong[Q[i].u],belong[Q[i].v]);
        }
    }
    for(int i=1;i<=tip;i++){
        if(!Q[i].od) continue;
        printf("%d\n",Q[i].ans);
    }
}
int main(){
//    freopen("a.in","r",stdin);
    init();
    Del_lk();
    work();
}