【洛谷 P4219】 [BJOI2014]大融合(LCT)

题目链接
维护子树信息向来不是(LCT)所擅长的，所以我没搞懂qwq
权当背背模板吧。Flash巨佬的blog里面写了虽然我没看懂。

#include <cstdio>
#define R register int
#define I inline void
#define lc c[x][0]
#define rc c[x][1]
const int MAXN = 300010;
inline int read(){
    int s = 0, w = 1;
    char ch = getchar();
    while(ch < '0' || ch > '9'){ if(ch == '-') w = -1; ch = getchar(); }
    while(ch >= '0' && ch <= '9'){ s = s * 10 + ch - '0'; ch = getchar(); }
    return s * w;
}
int f[MAXN], c[MAXN][2], v[MAXN], sz[MAXN], st[MAXN], tag[MAXN], ss[MAXN];
inline int nroot(R x){
	return c[f[x]][0] == x || c[f[x]][1] == x;
}
I pushup(R x){
	sz[x] = sz[lc] + sz[rc] + ss[x] + 1;
}
I pushdown(R x){
	if(tag[x]){
		R t = lc; lc = rc; rc = t;
		tag[lc] ^= 1; tag[rc] ^= 1; tag[x] = 0;
	}
}
I rotate(R x){
	R y = f[x], z = f[y], k = c[y][1] == x, w = c[x][!k];
	if(nroot(y)) c[z][c[z][1] == y] = x;
	c[x][!k] = y; c[y][k] = w; f[y] = x; f[x] = z;
	if(w) f[w] = y;
	pushup(y);
}
I pushall(R x){
    if(nroot(x)) pushall(f[x]);
    pushdown(x);
}
I splay(R x){
	pushall(x);
	while(nroot(x)) rotate(x);
	pushup(x);
}
I access(R x){
	for(R y = 0; x; x = f[y = x]){
	   splay(x); ss[x] += sz[rc]; ss[x] -= sz[rc = y]; pushup(x);
    }
}
I makeroot(R x){
	access(x); splay(x); 
	tag[x] ^= 1;
}
I split(R x, R y){
	makeroot(x); access(y); splay(y);
}
I link(R x, R y){
	split(x, y);
	ss[f[x] = y] += sz[x];
	pushup(y);
}
int n, m, a, b;
char opt;
int main(){
	n = read(); m = read();
	for(R i = 1; i <= n; ++i) sz[i] = 1;
	while(m--){
		opt = getchar(); while(opt != 'A' && opt != 'Q') opt = getchar();
		 a = read(); b = read();
		switch(opt){
			case 'Q' : split(a, b); printf("%lld
", (long long)(ss[a] + 1) * (ss[b] + 1)); break;
			case 'A' : link(a, b); break;
		}
	}
	return 0;
}