BZOJ #5457: 城市 [线段树合并]

线段树合并的板子题，每次从下到上合并就完事了

// by Isaunoya
#include <bits/stdc++.h>
using namespace std;
#define rep(i, j, n) for (int i = j; i <= n; i++)
#define in cin
#define out cout
#define pii pair<int, int>
#define fir first
#define sec second
int n, m;
const int maxn = 4e5 + 54;
int rt[maxn], ls[maxn << 5], rs[maxn << 5], cnt = 0;
pii mx[maxn << 5], ans[maxn];
void upd(int& p, int l, int r, int x, int v) {
  if (!p) p = ++cnt;
  if (l == r) {
    mx[p] = { v, -x };
    return;
  }
  int mid = l + r >> 1;
  if (x <= mid)
    upd(ls[p], l, mid, x, v);
  else
    upd(rs[p], mid + 1, r, x, v);
  mx[p] = max(mx[ls[p]], mx[rs[p]]);
}
int merge(int x, int y, int l, int r) {
  if (!x || !y) return x | y;
  if (l == r) {
    mx[x].fir += mx[y].fir;
    return x;
  }
  int mid = l + r >> 1;
  ls[x] = merge(ls[x], ls[y], l, mid);
  rs[x] = merge(rs[x], rs[y], mid + 1, r);
  mx[x] = max(mx[ls[x]], mx[rs[x]]);
  return x;
}
vector<int> g[maxn];
int fa[maxn];
void dfs(int u) {
  //  for (int v : g[u])
  //    if (fa[u] ^ v) fa[v] = u, dfs(v);
  for (int i = 0; i < g[u].size(); i++) {
    int v = g[u][i];
    if (fa[u] ^ v) {
      fa[v] = u;
      dfs(v);
    }
  }
  ans[u] = mx[rt[u]];
  rt[fa[u]] = merge(rt[fa[u]], rt[u], 1, n);
}
signed main() {
  // code begin.
  ios ::sync_with_stdio(false);
  cin.tie(0), cout.tie(0);
  in >> n >> m;
  rep(i, 2, n) {
    int u, v;
    in >> u >> v;
    g[u].push_back(v);
    g[v].push_back(u);
  }
  rep(i, 1, n) {
    int a, b;
    in >> a >> b;
    upd(rt[i], 1, n, a, b);
  }
  dfs(1);
  rep(i, 1, n) out << -ans[i].sec << ' ' << ans[i].fir << '
';
  return out.flush(), 0;
  // code end.
}