【Luogu】P3950部落冲突（树链剖分）

#include<cstdio>
#include<algorithm>
#include<cctype>
#include<cstring>
#include<cstdlib>
#define left (rt<<1)
#define right (rt<<1|1)
#define mid ((l+r)>>1)
#define lson l,mid,left
#define rson mid+1,r,right
#define maxn 300050
using namespace std;
inline long long read(){
    long long num=0,f=1;
    char ch=getchar();
    while(!isdigit(ch)){
        if(ch==‘-‘)    f=-1;
        ch=getchar();
    }
    while(isdigit(ch)){
        num=num*10+ch-‘0‘;
        ch=getchar();
    }
    return num*f;
}

struct Edge{
    int next,to;
}edge[maxn*3];
int head[maxn],num;
inline void add(int from,int to){
    edge[++num]=(Edge){head[from],to};
    head[from]=num;
}

int tree[maxn*4];
int dfn[maxn];
int deep[maxn];
int father[maxn];
int size[maxn];
int top[maxn];
int son[maxn];
int ID,n,m;

void unifnd(int x,int fa){
    deep[x]=deep[fa]+1;    size[x]=1;
    for(int i=head[x];i;i=edge[i].next){
        int to=edge[i].to;
        if(to==fa)    continue;
        father[to]=x;
        unifnd(to,x);
        size[x]+=size[to];
        if(son[x]==0||size[son[x]]<size[to])    son[x]=to;
    }
}

void unionn(int x,int Top){
    dfn[x]=++ID;    top[x]=Top;
    if(son[x]==0)    return;
    unionn(son[x],Top);
    for(int i=head[x];i;i=edge[i].next){
        int to=edge[i].to;
        if(to==father[x]||to==son[x])    continue;
        unionn(to,to);
    }
}

inline void pushup(int rt){
    tree[rt]=tree[left]+tree[right];
}

void update(int o,int num,int l,int r,int rt){
    if(l==r){
        tree[rt]+=num;
        return;
    }
    if(o<=mid)    update(o,num,lson);
    else        update(o,num,rson);
    pushup(rt);
    return;
}

int query(int from,int to,int l,int r,int rt){
    if(from<=l&&to>=r)    return tree[rt];
    int ans=0;
    if(from<=mid)    ans+=query(from,to,lson);
    if(to>mid)        ans+=query(from,to,rson);
    return ans;
}

struct War{
    int from,to;
}q[maxn];int cnt;

inline void adds(int from,int to){
    if(deep[from]<deep[to])    swap(from,to);
    q[++cnt]=(War){from,to};
    update(dfn[from],1,1,n,1);
    return;
}

inline void del(int rnk){
    int from=q[rnk].from;
    update(dfn[from],-1,1,n,1);
}

inline int LCA(int from,int to){
    while(top[from]!=top[to]){
        if(deep[top[from]]<deep[top[to]])    swap(from,to);
        from=father[top[from]];
    }
    if(deep[from]>deep[to])    swap(from,to);
    return from;
}

inline int ask(int from,int to){
    int lca=LCA(from,to),ans=-query(dfn[lca],dfn[lca],1,n,1);
    while(top[from]!=top[to]){
        if(deep[top[from]]<deep[top[to]])    swap(from,to);
        ans+=query(dfn[top[from]],dfn[from],1,n,1);
        if(ans>0)    return 0;
        from=father[top[from]];
    }
    if(deep[from]>deep[to])    swap(from,to);
    ans+=query(dfn[from],dfn[to],1,n,1);
    if(ans>0)    return 0;
    return 1;
}

int main(){
    n=read(),m=read();
    for(int i=1;i<n;++i){
        int x=read(),y=read();
        add(x,y);
        add(y,x);
    }
    unifnd(1,1);
    unionn(1,1);
    for(int i=1;i<=m;++i){
        char c[10];
        scanf("%s",c);
        if(c[0]==‘Q‘){
            int x=read(),y=read();
            if(ask(x,y))    printf("Yes\n");
            else            printf("No\n");
        }
        else if(c[0]==‘C‘){
            int x=read(),y=read();
            adds(x,y);
        }
        else{
            int x=read();
            del(x);
        }
    }
    return 0;
}