luogu 3690 【模板】 Link Cut Tree （动态树）

原来的代码有一些问题。

主要是对于不一定存在的边如何去判断，首先要保证在一个splay里，然后保证彼此之间直接联通且x的右儿子是空的

 #include<iostream>
 #include<cstdio>
 #include<cstring>
 #include<cstdlib>
 #include<cmath>
 #include<algorithm>
 #include<queue>
 #include<vector>
 #include<map>
 #include<set>
 #define ll long long
 #define inf 2139062143
 #define MAXN 300100
 #define MOD 998244353
 #define rep(i,s,t) for(register int i=(s),i##__end=(t);i<=i##__end;++i)
 #define dwn(i,s,t) for(register int i=(s),i##__end=(t);i>=i##__end;--i)
 #define ren for(register int i=fst[x];i;i=nxt[i])
 #define pb(i,x) vec[i].push_back(x)
 #define pls(a,b) (a+b)%MOD
 #define mns(a,b) (a-b+MOD)%MOD
 #define mul(a,b) (1LL*(a)*(b))%MOD
 using namespace std;
 inline int read()
 {
     int x=,f=;char ch=getchar();
     while(!isdigit(ch)) {if(ch=='-') f=-;ch=getchar();}
     while(isdigit(ch)) {x=x*+ch-'';ch=getchar();}
     return x*f;
 }
 int n,m;
 int ch[MAXN][],tag[MAXN],sum[MAXN],val[MAXN],fa[MAXN];
 struct Lct
 {
     int which(int x) {return ch[fa[x]][]==x;}
     int isroot(int x) {return ch[fa[x]][]!=x&&ch[fa[x]][]!=x;}
     void upd(int x) {sum[x]=val[x]^sum[ch[x][]]^sum[ch[x][]];}
     void rev(int x) {tag[x]^=;swap(ch[x][],ch[x][]);}
     void pshd(int x)
     {
         if(!tag[x]) return ;tag[x]^=;
         if(ch[x][]) rev(ch[x][]);
         if(ch[x][]) rev(ch[x][]);
     }
     void rotate(int x)
     {
         int f=fa[x],ff=fa[f],k=which(x);
         if(!isroot(f)) ch[ff][ch[ff][]==f]=x;fa[x]=ff;
         ch[f][k]=ch[x][k^],fa[ch[f][k]]=f,ch[x][k^]=f,fa[f]=x;
         upd(f);upd(x);
     }
     int st[MAXN],top;
     void splay(int x)
     {
         st[top=]=x;
         for(int i=x;!isroot(i);i=fa[i]) st[++top]=fa[i];
         dwn(i,top,) pshd(st[i]);
         for(int f;!isroot(x);rotate(x))
             if(!isroot(f=fa[x])) rotate(which(x)==which(f)?f:x);
     }
     void access(int x) {for(int t=;x;t=x,x=fa[x]){splay(x);ch[x][]=t;upd(x);}}
     void mkrt(int x) {access(x);splay(x);rev(x);}
     void link(int x,int y) {mkrt(x);fa[x]=y;}
     void split(int x,int y) {mkrt(x);access(y);splay(y);}
     int find(int x)
     {
         access(x);splay(x);
         while(ch[x][]) pshd(x),x=ch[x][];return x;
     }
     void cut(int x,int y) {split(x,y);if(fa[x]==y&&ch[y][]==x&&!ch[x][]) ch[y][]=fa[x]=,upd(y);}
 }lct;
 int main()
 {
     n=read(),m=read();int t,a,b;rep(i,,n) val[i]=read();
     while(m--)
     {
         t=read(),a=read(),b=read();
         if(!t) {lct.split(a,b);printf("%d\n",sum[b]);}
         if(t==&&lct.find(a)!=lct.find(b)) lct.link(a,b);
         if(t==&&lct.find(a)==lct.find(b)) lct.cut(a,b);
         if(t==) val[a]=b,splay(a);
     }
 }