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OI-codes/Gym/102439/K/K.cpp

149 lines
2.6 KiB
C++

#include <iostream>
#include <cmath>
#include <string>
#include <vector>
using std::cin;
using std::cout;
using std::endl;
const int N = 2e5 + 5;
const int mod = 1e9 + 7;
int n, m, a[N], f[N];
int cnt, id[N], rid[N], fa[N], dep[N], siz[N], son[N], top[N];
std::vector<std::pair<int, int>> g[N];
struct node {
int l, r, v, max, sum;
node() = default;
node(int _l, int _r)
: l(_l), r(_r), v(0), max(0), sum(0) {}
} tr[N << 2];
void pushup(int u) {
tr[u].max = std::max(tr[u << 1].max, tr[u << 1 | 1].max);
tr[u].sum = (tr[u << 1].sum + tr[u << 1 | 1].sum) % mod;
}
void build(int u, int l, int r) {
tr[u] = node(l, r);
if (l == r) {
tr[u].max = a[rid[l]];
tr[u].sum = static_cast<long long>(tr[u].max) * f[rid[l]] % mod;
return;
}
int mid = l + r >> 1;
build(u << 1, l, mid);
build(u << 1 | 1, mid + 1, r);
pushup(u);
}
void dfs1(int u, int f) {
fa[u] = f;
dep[u] = dep[f] + 1;
siz[u] = 1;
for (auto e : g[u]) {
int v = e.first,
w = e.second;
if (v == f) continue;
a[v] = w;
dfs1(v, u);
siz[u] += siz[v];
if (siz[son[u]] < siz[v]) son[u] = v;
}
::f[u] = static_cast<long long>(siz[u]) * (n - siz[u]) % mod;
}
void dfs2(int u, int t) {
rid[id[u] = ++cnt] = u;
top[u] = t;
if (!son[u]) return;
dfs2(son[u], t);
for (auto e : g[u]) {
int v = e.first;
if (v == fa[u]) continue;
if (v == son[u]) continue;
dfs2(v, v);
}
}
void modify(int u, int l, int r) {
if (tr[u].max <= 1) return;
if (tr[u].l == tr[u].r) {
tr[u].max = std::sqrt(tr[u].max);
tr[u].sum = static_cast<long long>(tr[u].max) * f[rid[tr[u].l]] % mod;
return;
}
int mid = tr[u].l + tr[u].r >> 1;
if (l <= mid) modify(u << 1, l, r);
if (r > mid) modify(u << 1 | 1, l, r);
pushup(u);
}
void modify_path(int u, int v) {
while (top[u] != top[v]) {
if (dep[top[u]] < dep[top[v]]) std::swap(u, v);
modify(1, id[top[u]], id[u]);
u = fa[top[u]];
}
if (u == v) return;
if (dep[u] < dep[v]) std::swap(u, v);
modify(1, id[v] + 1, id[u]);
}
int main() {
std::ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n >> m;
for (int i = 1, u, v, w; i < n; i++) {
cin >> u >> v >> w;
g[u].emplace_back(v, w);
g[v].emplace_back(u, w);
}
dfs1(1, 1);
dfs2(1, 1);
build(1, 1, n);
cout << tr[1].sum << endl;
while (m--) {
int u, v;
cin >> u >> v;
modify_path(u, v);
cout << tr[1].sum << endl;
}
return 0;
}