HYSBZ - 1036 树的统计Count（树剖）

#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int N = 30010;
const int M = 30010 << 2;
const int INF = 0x3f3f3f3f;

struct Edge{
int u, v, next;
Edge() {}
Edge(int u, int v, int next): u(u), v(v), next(next) {}
}E[N * 2];

int n, q, tot, idx;
int top
, size
, f
, son
, dep
, id
, head
, val
, weight
, Sum[M], Max[M];
bool flag;

void build(int u, int l, int r) {
if (l == r) {
Max[u] = Sum[u] = val[l];
return ;
}

int mid = (l + r) >> 1;
build(2 * u, l, mid);
build(2 * u + 1, mid + 1, r);
Sum[u] = Sum[2 * u] + Sum[2 * u + 1];
Max[u] = max(Max[2 * u], Max[2 * u + 1]);
}

void dfs1(int u, int fa, int depth) {
dep[u] = depth; size[u] = 1; son[u] = 0; f[u] = fa;
for (int i = head[u]; ~i; i = E[i].next) {
int v = E[i].v;
if (v == fa) continue;
dfs1(v, u, depth + 1);
size[u] += size[v];
if (size[son[u]] < size[v]) son[u] = v;
}
}

void dfs2(int u, int tp) {
top[u] = tp;
id[u] = ++idx;
if (son[u]) dfs2(son[u], tp);
for (int i = head[u]; ~i; i = E[i].next) {
int v = E[i].v;
if (v == f[u] || v == son[u]) continue;
dfs2(v, v);
}
}

void add(int u, int l, int r, int pos, int c) {
if (l == r && l == pos) {
Sum[u] = Max[u] = c;
return ;
}
int mid = (l + r) >> 1;
if (pos <= mid) add(2 * u, l, mid, pos, c);
else add(2 * u + 1, mid + 1, r, pos, c);
Sum[u] = Sum[2 * u] + Sum[2 * u + 1];
Max[u] = max(Max[2 * u], Max[2 * u + 1]);
}

int query(int u, int l, int r, int L, int R) {
if (L <= l && r <= R) {
if (flag) return Sum[u];
else return Max[u];
}

int mid = (l + r) >> 1;
int ans = -INF, tmp;
if (flag) ans = 0;

if (L <= mid) {
tmp = query(2 * u, l, mid, L, R);
if (flag) ans += tmp;
else ans = max(ans, tmp);
}

if (R > mid) {
tmp = query(2 * u + 1, mid + 1, r, L, R);
if (flag) ans += tmp;
else ans = max(ans, tmp);
}

return ans;
}

int gao(int u, int v) {
int ans = -INF, tmp;
if (flag) ans = 0;

int tp1 = top[u], tp2 = top[v];
while (tp1 != tp2) {
if (dep[tp1] < dep[tp2]) {
swap(tp1, tp2);
swap(u, v);
}
tmp = query(1, 1, idx, id[tp1], id[u]);
if (flag) ans += tmp;
else ans = max(ans, tmp);
u = f[tp1];
tp1 = top[u];
}

if (dep[u] > dep[v]) swap(u, v);
tmp = query(1, 1, idx, id[u], id[v]);
if (flag) ans += tmp;
else ans = max(ans, tmp);
return ans;
}

void solve() {
char op[30];
int a, b;
scanf("%d", &q);
while (q--) {
scanf("%s%d%d", op, &a, &b);
if (op[0] == 'C') add(1, 1, idx, id[a], b);
else {
flag = false;
if (op[1] == 'S') flag = true;
printf("%d\n", gao(a, b));
}
}
}

void AddEdge(int u, int v) {
E[tot] = Edge(u, v, head[u]);
head[u] = tot++;
E[tot] = Edge(v, u, head[v]);
head[v] = tot++;
}

void init() {
memset(head, -1, sizeof(head));
tot = idx = 0;

int u, v;
for (int i = 1; i < n; i++) {
scanf("%d%d", &u, &v);
AddEdge(u, v);
}

dfs1(1, 0, 1);
dfs2(1, 1);
for (int i = 1; i <= n; i++)
scanf("%d", &val[id[i]]);
build(1, 1, idx);
}

int main() {
while (scanf("%d", &n) != EOF) {
init();
solve();
}
return 0;
}