傳送門 lct模板題。 學習了新姿勢： 判斷一條邊是否已經存在的方法。 感覺其它都跟洞穴勘探差不多。 程式碼：

#include<bits/stdc++.h>
#define N 300005
using namespace std;
inline int read(){
	int ans=0;
	char ch=getchar();
	while(!isdigit(ch))ch=getchar();
	while(isdigit(ch))ans=(ans<<3)+(ans<<1)+(ch^48),ch=getchar();
	return ans; 
}
int n,
 
m,a[N],stk[N],top,son[N][2],sum[N],rev[N],fa[N];
inline int which(int x){return x==son[fa[x]][1];}
inline int isroot(int x){return !fa[x]||(son[fa[x]][0]!=x&&son[fa[x]][1]!=x);}
inline void pushup(int p){sum[p]=sum[son[p][0]]^sum[son[p][1]]^a[p];}
inline void pushdown(int p){
	if(!rev[p])return
 
;
	swap(son[p][0],son[p][1]),rev[p]^=1;
	if(son[p][0])rev[son[p][0]]^=1;
	if(son[p][1])rev[son[p][1]]^=1;
}
inline void rotate(int x){
	int y=fa[x],z=fa[y],t=which(x);
	if(z&&!isroot(y))son[z][which(y)]=x;
	fa[y]=x,fa[x]=z,son[y][t]=son[x][t^1],son[x][t^1]=y;
	if(son[y][t])fa[son[y][t]]=y;
	pushup
 
(y),pushup(x);
}
inline void splay(int x){
	stk[top=1]=x;
	for(int i=x;!isroot(i);i=fa[i])stk[++top]=fa[i];
	while(top)pushdown(stk[top--]);
	while(!isroot(x)){if(!isroot(fa[x]))rotate(which(x)==which(fa[x])?fa[x]:x);rotate(x);}
}
inline void access(int x){for(int y=0;x;y=x,x=fa[x])splay(x),son[x][1]=y,pushup(x);}
inline void makeroot(int x){access(x),splay(x),rev[x]^=1,pushdown(x);}
inline int findroot(int x){
	access(x),splay(x);
	while(pushdown(x),son[x][0])x=son[x][0];
	return splay(x),x;
}
inline void link(int x,int y){makeroot(x),fa[x]=y,pushup(y);}
inline void cut(int x,int y){makeroot(x),access(y),splay(y),son[y][0]=fa[x]=0,pushup(y);}
inline int query(int x,int y){return makeroot(x),access(y),splay(y),sum[y];}
int main(){
	n=read(),m=read();
	for(int i=1;i<=n;++i)a[i]=read();
	while(m--){
		int op=read(),x=read(),y=read();
		switch(op){
			case 0:printf("%d\n",query(x,y));break;
			case 1:{if(findroot(x)!=findroot(y))link(x,y);break;}
			case 2:{if(makeroot(x),access(y),!son[son[y][0]][1]&&!son[son[y][0]][0])cut(x,y);break;}
			default:splay(x),a[x]=y;
		}
	}
	return 0;
}