【BZOJ 1036】【ZJOI 2008】树的统计Count

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;

const int N = 30003;

int n;
struct node *null;
struct node {
node *fa, *ch[2];
int w, sum, ma, rev;
bool pl() {return fa->ch[1] == this;}
bool check() {return fa == null || (fa->ch[0] != this && fa->ch[1] != this);}
void setc(node *r, int c) {ch[c] = r; if (r != null) r->fa = this;}
void count() {
sum = ch[0]->sum + ch[1]->sum + w;
ma = w;
if (ch[0] != null) ma = max(ma, ch[0]->ma);
if (ch[1] != null) ma = max(ma, ch[1]->ma);
}
void push() {if (rev) {swap(ch[0], ch[1]); rev = 0; ch[0]->rev ^= 1; ch[1]->rev ^= 1;}}
} pool
;

namespace LCT {
void rotate(node *r) {
node *f = r->fa;
int c = r->pl();
if (f->check()) r->fa = f->fa;
else f->fa->setc(r, f->pl());
f->setc(r->ch[c ^ 1], c);
r->setc(f, c ^ 1);
f->count();
}

void update(node *r) {if (!r->check()) update(r->fa); r->push();}

void splay(node *r) {
update(r);
for (; !r->check(); rotate(r))
if (!r->fa->check()) rotate(r->pl() == r->fa->pl() ? r->fa : r);
r->count();
}

node *access(node *r) {
node *y = null;
while (r != null) {
splay(r);
r->ch[1] = y;
y = r; r = r->fa;
}
return y;
}

void changeroot(node *r) {access(r)->rev ^= 1; splay(r);}
void link(node *r, node *t) {changeroot(r); r->fa = t;}
int query_max(node *u, node *v) {changeroot(u); access(v); splay(v); return v->ma;}
int query_sum(node *u, node *v) {changeroot(u); access(v); splay(v); return v->sum;}

int x
, y
;
void init() {
null = &pool[0];
null->fa = null->ch[0] = null->ch[1] = null;
null->ma = null->sum = null->rev = null->w = 0;

scanf("%d", &n);
for (int i = 1; i < n; ++i) scanf("%d%d", x + i, y + i);
for (int i = 1; i <= n; ++i) {
pool[i].fa = pool[i].ch[0] = pool[i].ch[1] = null;
pool[i].rev = 0;
scanf("%d", &pool[i].w);
pool[i].ma = pool[i].sum = pool[i].w;
}

for (int i = 1; i < n; ++i) link(&pool[x[i]], &pool[y[i]]);
}
}

int main() {
LCT::init();

int q, u, v;
char s[18];
scanf("%d", &q);
while (q--) {
scanf("%s%d%d", s, &u, &v);
if (s[0] == 'C') {
LCT::splay(&pool[u]);
pool[u].w = pool[u].ma = pool[u].sum = v;
} else {
if (s[1] == 'M') printf("%d\n", LCT::query_max(&pool[u], &pool[v]));
else printf("%d\n", LCT::query_sum(&pool[u], &pool[v]));
}
}
return 0;
}