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