BZOJ 3282 Link Cut Tree (LCT)

题目大意：维护一个森林，支持边的断，连，修改某个点的权值，求树链所有点点权的异或和

洛谷P3690传送门

搞了一个下午终于明白了LCT的原理

 #include <cstdio>
 #include <algorithm>
 #include <cstring>
 #define root d[0].ch[1]
 #define il inline
 #define nu 7777
 #define inf 500000
 #define N 300100
 using namespace std;

 int n,m,tp;
 int stk[N];
 char str[];
 struct Link_Cut_Tree{
     int fa[N],ch[N][],sum[N],val[N],rev[N];
     il int idf(int x){return ch[fa[x]][]==x?:;}
     il int isroot(int x){return (ch[fa[x]][]!=x&&ch[fa[x]][]!=x)?:;}
     il void con(int x,int ff,int p){fa[x]=ff;ch[ff][p]=x;}
     il void pushup(int x){sum[x]=sum[ch[x][]]^sum[ch[x][]]^val[x];}
     il void revers(int x){swap(ch[x][],ch[x][]),rev[x]^=;}
     il void pushdown(int x){
         if(rev[x]){
             if(ch[x][]) revers(ch[x][]);
             if(ch[x][]) revers(ch[x][]);
             rev[x]=;}}
     il void rot(int x){
         int y=fa[x];int ff=fa[y];int px=idf(x);int py=idf(y);
         if(!isroot(y)) ch[ff][py]=x;
         fa[x]=ff,con(ch[x][px^],y,px),con(y,x,px^);
         pushup(y),pushup(x);}
     void splay(int x){
         int y=x;stk[++tp]=x;
         while(!isroot(y)){stk[++tp]=fa[y];y=fa[y];}
         while(tp){pushdown(stk[tp--]);}
         while(!isroot(x)){
             y=fa[x];
             if(isroot(y)) rot(x);
             else if(idf(y)==idf(x)) rot(y),rot(x);
             else rot(x),rot(x);
         }}
     il void access(int x){for(int y=;x;y=x,x=fa[x])splay(x),ch[x][]=y,pushup(x);}
     il void mkroot(int x){access(x),splay(x),revers(x);}
     il int findrt(int x){
         access(x),splay(x);
         while(ch[x][])pushdown(x),x=ch[x][];
         return x;}
     il void split(int x,int y){mkroot(x),access(y),splay(y);}
     il void link(int x,int y){mkroot(x);if(findrt(y)!=x)fa[x]=y;}
     il void cut(int x,int y){
         mkroot(x);
         if(findrt(y)==x&&fa[x]==y&&!ch[x][])
             fa[x]=ch[y][]=,pushup(y);}
 }lct;

 int gc()
 {
     int rett=,fh=;char c=getchar();
     while(c<''||c>''){if(c=='-')fh=-;c=getchar();}
     while(c>=''&&c<=''){rett=(rett<<)+(rett<<)+c-'';c=getchar();}
     return rett*fh;
 }

 int main()
 {
     n=gc(),m=gc();
     for(int i=;i<=n;i++) lct.val[i]=gc();
     int fl,x,y;
     for(int i=;i<=m;i++)
     {
         fl=gc(),x=gc(),y=gc();
         if(fl==) lct.split(x,y),printf("%d\n",lct.sum[y]);
         if(fl==) lct.link(x,y);
         if(fl==) lct.cut(x,y);
         if(fl==) lct.splay(x),lct.val[x]=y,lct.pushup(x);
     }
     return ;
 }