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| #include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <vector>
#include <string>
#include <utility>
#ifdef XLor
#define dbg(args...) do { cout << #args << " -> "; err(args); } while (0)
void err() { std::cout << std::endl; }
template<typename T, typename...Args>
void err(T a, Args...args) { std::cout << a << ' '; err(args...); }
#else
#define dbg(...)
#endif
#define lson l, m, rt << 1
#define rson m + 1, r, rt << 1 | 1
#define ms(a,b) memset(a,b,sizeof(a))
using namespace std;
typedef long long ll;
typedef pair<int,int> PII;
const int mod = 998244353;
const int inf = 1 << 30;
const int maxn = 100000 + 5;
struct Edge {
int u, v, w;
} eg[maxn];
vector<PII> edge[maxn];
int n, q, tin[maxn], tout[maxn], rid[maxn], tot;
namespace hld {
struct BIT {
ll a[maxn];
inline int lowbit(int x) {
return x & -x;
}
inline void update(int i, int x) {
for (; i <= n; i += lowbit(i)) a[i] += x;
}
inline void update(int l, int r, int x) {
update(l, x); update(r + 1, -x);
}
inline ll query(int i) {
ll r = 0;
for (; i; i -= lowbit(i)) r += a[i];
return r;
}
} g;
int siz[maxn], dep[maxn], fa[maxn], son[maxn], top[maxn];
void dfs(int u, int f) {
tin[u] = ++tot; rid[tot] = u;
dep[u] = dep[f] + 1; fa[u] = f; siz[u] = 1; son[u] = 0;
int m = -1;
for (auto& x: edge[u]) {
int v = x.first;
if (v == f) continue;
dfs(v, u);
g.update(tin[v], tout[v], x.second);
siz[u] += siz[v];
if (siz[v] > m) son[u] = v, m = siz[v];
}
tout[u] = tot;
}
void dfs(int u, int f, int tp) {
top[u] = tp;
if (!son[u]) return;
dfs(son[u], u, tp); // !
for (auto& x: edge[u]) {
int v = x.first;
if (v == f || v == son[u]) continue; // !
dfs(v, u, v);
}
}
void build() {
dfs(1, 0); dfs(1, 0, 1);
}
int qlca(int u, int v) {
while (top[u] != top[v]){
if (dep[top[u]] < dep[top[v]]) swap(u, v);
u = fa[top[u]];
}
return dep[u] < dep[v] ? u : v;
}
ll qdis(int u, int v) {
ll r = g.query(tin[u]) + g.query(tin[v]);
int l = qlca(u, v);
return r - 2ll * g.query(tin[l]);
}
}
using hld::qdis;
struct Node {
int u, v; ll d;
} a[maxn << 2];
void pushup(int rt) {
if (a[rt << 1].d > a[rt << 1 | 1].d) {
a[rt] = a[rt << 1];
} else {
a[rt] = a[rt << 1 | 1];
}
int x = a[rt << 1].u, y = a[rt << 1].v;
int u = a[rt << 1 | 1].u, v = a[rt << 1 | 1].v;
ll tot;
if ((tot = qdis(x, u)) > a[rt].d) a[rt] = (Node){ x, u, tot };
if ((tot = qdis(x, v)) > a[rt].d) a[rt] = (Node){ x, v, tot };
if ((tot = qdis(y, u)) > a[rt].d) a[rt] = (Node){ y, u, tot };
if ((tot = qdis(y, v)) > a[rt].d) a[rt] = (Node){ y, v, tot };
}
void build(int l = 1, int r = n, int rt = 1) {
if (l == r) {
int u = rid[l];
a[rt] = (Node){ u, u, 0 };
return ;
}
int m = (l + r) / 2;
build(lson); build(rson);
pushup(rt);
}
void update(int L, int R, int l = 1, int r = n, int rt = 1) {
if (L <= l && r <= R) return ;
int m = (l + r) / 2;
if (L <= m) update(L, R, lson);
if (R > m) update(L, R, rson);
pushup(rt);
}
int main() {
scanf("%d", &n);
for (int i = 1; i < n; i++) {
scanf("%d%d%d", &eg[i].u, &eg[i].v, &eg[i].w);
edge[eg[i].u].push_back({ eg[i].v, eg[i].w });
edge[eg[i].v].push_back({ eg[i].u, eg[i].w });
}
hld::build(); build();
scanf("%d", &q);
char op[5]; int e, v, w;
for (int i = 1; i <= q; i++) {
scanf("%s", op);
if (op[0] == 'C') {
scanf("%d%d", &e, &w);
int u = eg[e].u, v = eg[e].v, ww = eg[e].w;
if (hld::fa[v] != u) swap(u, v);
hld::g.update(tin[v], tout[v], w - ww);
eg[e].w = w;
update(tin[v], tout[v]);
} else if (op[0] == 'Q') {
scanf("%d", &v);
int x = a[1].u, y = a[1].v;
// dbg(x, y, a[1].d);
printf("%lld\n", max(qdis(x, v), qdis(y, v)));
}
}
return 0;
}
|