题目大意:略。
解题思路:树链剖分+线段树维护。
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
const int maxn = 30005;
const int INF = 0x3f3f3f3f;
#define lson(x) ((x)<<1)
#define rson(x) (((x)<<1)|1)
int lc[maxn << 2], rc[maxn << 2], s[maxn << 2], m[maxn << 2], val[maxn];
inline void pushup(int u) {
s[u] = s[lson(u)] + s[rson(u)];
m[u] = max(m[lson(u)], m[rson(u)]);
}
void build (int u, int l, int r) {
lc[u] = l;
rc[u] = r;
if (l == r) {
s[u] = m[u] = val[l];
return;
}
int mid = (l + r) / 2;
build(lson(u), l, mid);
build(rson(u), mid + 1, r);
pushup(u);
}
void modify(int u, int x, int w) {
if (lc[u] == x && rc[u] == x) {
s[u] = m[u] = w;
return;
}
int mid = (lc[u] + rc[u]) / 2;
if (x <= mid)
modify(lson(u), x, w);
else
modify(rson(u), x, w);
pushup(u);
}
int sum(int u, int l, int r) {
if (l <= lc[u] && rc[u] <= r)
return s[u];
int mid = (lc[u] + rc[u]) / 2, ret = 0;
if (l <= mid)
ret += sum(lson(u), l, r);
if (r > mid)
ret += sum(rson(u), l, r);
return ret;
}
int query(int u, int l, int r) {
if (l <= lc[u] && rc[u] <= r)
return m[u];
int mid = (lc[u] + rc[u]) / 2, ret = -INF;
if (l <= mid)
ret = max(ret, query(lson(u), l, r));
if (r > mid)
ret = max(ret, query(rson(u), l, r));
return ret;
}
int N, Q, ne, first[maxn], jump[maxn * 2], link[maxn * 2];
int id, idx[maxn], far[maxn], son[maxn], cnt[maxn], top[maxn], dep[maxn];
inline void add_Edge (int u, int v) {
link[ne] = v;
jump[ne] = first[u];
first[u] = ne++;
}
void dfs_fir (int u, int pre, int d) {
far[u] = pre;
dep[u] = d;
son[u] = 0;
cnt[u] = 1;
for (int i = first[u]; i + 1; i = jump[i]) {
int v = link[i];
if (v == pre)
continue;
dfs_fir(v, u, d + 1);
cnt[u] += cnt[v];
if (cnt[son[u]] < cnt[v])
son[u] = v;
}
}
void dfs_sec(int u, int rot) {
top[u] = rot;
idx[u] = ++id;
if (son[u])
dfs_sec(son[u], rot);
for (int i = first[u]; i + 1; i = jump[i]) {
int v = link[i];
if (v == far[u] || v == son[u])
continue;
dfs_sec(v, v);
}
}
void init () {
int u, v;
id = ne = 0;
memset(first, -1, sizeof(first));
for (int i = 1; i < N; i++) {
scanf("%d%d", &u, &v);
add_Edge(u, v);
add_Edge(v, u);
}
dfs_fir(1, 0, 1);
dfs_sec(1, 1);
for (int i = 1; i <= N; i++)
scanf("%d", &val[idx[i]]);
build(1, 1, N);
}
int solve_query(int u, int v) {
int p = top[u], q = top[v], ret = -INF;
while (p != q) {
if (dep[p] < dep[q]) {
swap(p, q);
swap(u, v);
}
ret = max(ret, query(1, idx[p], idx[u]));
u = far[p];
p = top[u];
}
if (dep[u] > dep[v])
swap(u, v);
ret = max(ret, query(1, idx[u], idx[v]));
return ret;
}
int solve_sum(int u, int v) {
int p = top[u], q = top[v], ret = 0;
while (p != q) {
if (dep[p] < dep[q]) {
swap(p, q);
swap(u, v);
}
ret += sum(1, idx[p], idx[u]);
u = far[p];
p = top[u];
}
if (dep[u] > dep[v])
swap(u, v);
ret += sum(1, idx[u], idx[v]);
return ret;
}
int main () {
while (scanf("%d", &N) == 1) {
init();
int u, v;
char op[10];
scanf("%d", &Q);
while (Q--) {
scanf("%s%d%d", op, &u, &v);
if (op[0] == 'C')
modify(1, idx[u], v);
else if (op[1] == 'M')
printf("%d\n", solve_query(u, v));
else
printf("%d\n", solve_sum(u, v));
}
}
return 0;
}