P3690 【模板】Link Cut Tree （动态树）
https://www.luogu.org/problemnew/show/P3690
分析：
LCT模板
代码：
注意一下cut！
1 #include<bits/stdc++.h> 2 using namespace std; 3 typedef long long LL; 4 5 char buf[100000],*_p1 = buf,*_p2 = buf; 6 #define nc() (_p1==_p2&&(_p2=(_p1=buf)+fread(buf,1,100000,stdin),_p1==_p2) ? EOF :*_p1++) 7 inline int read() { 8 int x=0,f=1;char ch=nc();for(;!isdigit(ch);ch=nc())if(ch=='-')f=-1; 9 for (;isdigit(ch);ch=nc())x=x*10+ch-'0';return x*f; 10 } 11 12 const int N = 300100; 13 14 int val[N],fa[N],ch[N][2],rev[N],sum[N],sk[N],Top; 15 16 inline void pushup(int x) { 17 sum[x] = sum[ch[x][0]] ^ sum[ch[x][1]] ^ val[x]; 18 } 19 inline void pushdown(int x) { 20 if (rev[x]) { 21 rev[ch[x][0]] ^= 1; rev[ch[x][1]] ^= 1; 22 swap(ch[x][0], ch[x][1]); 23 rev[x] ^= 1; 24 } 25 } 26 inline bool isroot(int x) { 27 return ch[fa[x]][0] != x && ch[fa[x]][1] != x; 28 } 29 inline int son(int x) { 30 return x == ch[fa[x]][1]; 31 } 32 inline void rotate(int x) { 33 int y = fa[x],z = fa[y],b = son(x),c = son(y),a = ch[x][!b]; 34 if (!isroot(y)) ch[z][c] = x;fa[x] = z; 35 ch[x][!b] = y;fa[y] = x; 36 ch[y][b] = a;if (a) fa[a] = y; 37 pushup(y);pushup(x); 38 } 39 inline void splay(int x) { 40 sk[Top = 1] = x; 41 for (int i=x; !isroot(i); i=fa[i]) sk[++Top] = fa[i]; 42 while (Top) pushdown(sk[Top--]); 43 while (!isroot(x)) { 44 int y = fa[x]; 45 if (isroot(y)) rotate(x); 46 else { 47 if (son(x) == son(y)) rotate(y), rotate(x); 48 else rotate(x), rotate(x); 49 } 50 } 51 } 52 inline void access(int x) { 53 for (int last=0; x; last=x, x=fa[x]) { 54 splay(x); ch[x][1] = last; pushup(x); 55 } 56 } 57 inline void makeroot(int x) { 58 access(x); splay(x); rev[x] ^= 1; 59 } 60 inline int find(int x) { 61 access(x); splay(x); 62 while (ch[x][0]) x = ch[x][0]; 63 return x; 64 } 65 inline void link(int x,int y) { 66 makeroot(x); 67 fa[x] = y; 68 } 69 inline void cut(int x,int y) { 70 makeroot(x); access(y); splay(y); 71 if (fa[x] == y && !ch[x][1]) fa[x] = ch[y][0] = 0; 72 } 73 inline void update(int x,int y) { 74 makeroot(x);val[x] = y;pushup(x); 75 } 76 inline int query(int x,int y) { 77 makeroot(x);access(y);splay(y); 78 return sum[y]; 79 } 80 int main() { 81 int n = read(),m = read(),opt,x,y; 82 for (int i=1; i<=n; ++i) sum[i] = val[i] = read(); 83 while (m--) { 84 opt = read(),x = read(),y = read(); 85 if (opt==0) printf("%d ",query(x,y)); 86 else if (opt==1) { 87 if (find(x)!=find(y)) link(x,y); 88 } 89 else if (opt==2) { 90 if (find(x)==find(y)) cut(x,y); 91 } 92 else update(x,y); 93 } 94 return 0; 95 }