[luogu3950] 部落冲突 - Link Cut Tree

有了LCT这不就是思博题了吗

#include <bits/stdc++.h>
using namespace std;

const int N = 1000000;

int n,m,t1,t2,t3;
char op[5];

struct LinkCutTree {
    int top, q[N], ch[N][2], fa[N], rev[N];
    inline void pushup(int x) {

    }
    inline void pushdown(int x) {
        if(!rev[x])
            return;
        rev[ch[x][0]]^=1;
        rev[ch[x][1]]^=1;
        rev[x]^=1;
        swap(ch[x][0],ch[x][1]);
    }
    inline bool isroot(int x) {
        return ch[fa[x]][0]!=x && ch[fa[x]][1]!=x;
    }
    inline void rotate(int p) {
        int q=fa[p], y=fa[q], x=ch[fa[p]][1]==p;
        ch[q][x]=ch[p][x^1];
        fa[ch[q][x]]=q;
        ch[p][x^1]=q;
        fa[q]=p;
        fa[p]=y;
        if(y)
            if(ch[y][0]==q)
                ch[y][0]=p;
            else  if(ch[y][1]==q)
                ch[y][1]=p;
        pushup(q);
        pushup(p);
    }
    inline void splay(int x) {
        q[top=1]=x;
        for(int i=x; !isroot(i); i=fa[i])
            q[++top]=fa[i];
        for(int i=top; i; i--)
            pushdown(q[i]);
        for(; !isroot(x); rotate(x))
            if(!isroot(fa[x]))
                rotate((ch[fa[x]][0]==x)==(ch[fa[fa[x]]][0]==fa[x])?fa[x]:x);
    }
    void access(int x) {
        for(int t=0; x; t=x,x=fa[x])
            splay(x),ch[x][1]=t,pushup(x);
    }
    void makeroot(int x) {
        access(x);
        splay(x);
        rev[x]^=1;
    }
    int find(int x) {
        access(x);
        splay(x);
        while(ch[x][0])
            x=ch[x][0];
        return x;
    }
    void split(int x,int y) {
        makeroot(x);
        access(y);
        splay(y);
    }
    void cut(int x,int y) {
        split(x,y);
        if(ch[y][0]==x)
            ch[y][0]=0, fa[x]=0;
    }
    void link(int x,int y) {
        makeroot(x);
        fa[x]=y;
    }
} tree;

vector <pair<int,int> > vc;

int main() {
    scanf("%d%d",&n,&m);
    for(int i=1; i<n; i++) {
        scanf("%d%d",&t1,&t2);
        tree.link(t1,t2);
    }
    for(int i=1; i<=m; i++) {
        scanf("%s",op);
        if(op[0]=='Q') {
            scanf("%d%d",&t1,&t2);
            if(tree.find(t1) == tree.find(t2))
                printf("Yes\n");
            else
                printf("No\n");
        }
        if(op[0]=='C') {
            scanf("%d%d",&t1,&t2);
            tree.cut(t1,t2);
            vc.push_back(make_pair(t1,t2));
        }
        if(op[0]=='U') {
            scanf("%d",&t1);
            t2=vc[t1-1].first, t3=vc[t1-1].second;
            tree.link(t2,t3);
        }
    }
}