认父不认子的lct
注意：不 要 把 $fa[x]$和$nrt(x)$ 混 在 一 起 ！
#include<cstdio> void swap(int &a,int &b){a^=b^=a^=b;} #define N 300005 int n,m,s[N],v[N],ch[2][N],fa[N],rev[N]; #define lc ch[0][x] #define rc ch[1][x] bool nrt(int x){return ch[0][fa[x]]==x||ch[1][fa[x]]==x;} void up(int x){s[x]=s[lc]^v[x]^s[rc];} void Rev(int x){swap(lc,rc);rev[x]^=1;} void down(int x){if(rev[x])Rev(lc),Rev(rc),rev[x]=0;} void fadown(int x){if(nrt(x))fadown(fa[x]); down(x);} void turn(int x){ int y=fa[x],z=fa[y],l=(ch[1][y]==x),r=l^1; if(nrt(y)) ch[ch[1][z]==y][z]=x; fa[ch[r][x]]=y; fa[x]=z; fa[y]=x; ch[l][y]=ch[r][x]; ch[r][x]=y; up(y); up(x); } void splay(int x){ fadown(x); for(;nrt(x);turn(x)){ int y=fa[x],z=fa[y]; if(nrt(y)) turn((ch[1][y]==x)^(ch[1][z]==y)?x:y); } } void access(int x){for(int y=0;x;y=x,x=fa[x])splay(x),rc=y,up(x);}//构造一棵splay，把当前树根与x用重边连起来 void makert(int x){access(x);splay(x);Rev(x);}//总树根改为x int find(int x){//找x所在树的树根 access(x);splay(x);down(x); while(lc) x=lc,down(x); splay(x); return x; } void link(int x,int y){makert(x); if(find(y)!=x)fa[x]=y;} void cut(int x,int y){ makert(x); if(find(y)==x&&fa[y]==x&&!ch[0][y]) rc=fa[y]=0,up(x); } void split(int x,int y){makert(x);access(y);splay(y);}//拉出一条x-y的路径成为一个根为y的splay int main(){ scanf("%d%d",&n,&m); int q1,q2,q3; for(int i=1;i<=n;++i) scanf("%d",&v[i]); while(m--){ scanf("%d%d%d",&q1,&q2,&q3); if(q1==0) split(q2,q3),printf("%d ",s[q3]); else if(q1==1) link(q2,q3); else if(q1==2) cut(q2,q3); else splay(q2),v[q2]=q3; }return 0; }